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排序方式: 共有785条查询结果,搜索用时 31 毫秒
51.
Fluorescent molecular thermometers based on polymers showing a temperature-induced phase transition and labeled with polarity-sensitive fluorescent benzofurazans are the most sensitive known. Here we show a simple and effective method for modulating the sensitive temperature ranges of fluorescent molecular thermometers based on such temperature-responsive polymers. 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole was adopted as a polarity-sensitive fluorescent benzofurazan, and nine copolymers of two kinds of acrylamide derivative (N-n-propylacrylamide, N-isopropylacrylamide, and/or N-isopropylmethacrylamide) with a small amount of DBD-AE were obtained. The fluorescence intensities of these copolymers in aqueous solution sharply increased with increasing temperature over a small range (6-7 degrees C). In contrast, these fluorescent molecular thermometers differed from one another in the sensitive temperature range (between 20 and 49 degrees C). Moreover, the sensitive temperature ranges were well related to the acrylamide ratios in feed. In addition, the responses from these fluorescent molecular thermometers to the change in temperature were reversible and exactly repeatable during 10 cycles of heating and cooling (relative standard deviation of the fluorescence intensity, 0.44-1.0%). 相似文献
52.
Kasamatsu M. Tsukamoto K. Shiratori S. Obara A. Uchiyama F. 《Quantum Electronics, IEEE Journal of》1982,18(2):173-175
A high-power CW TE CO2 laser using a new graphite anode structure and a novel Mo wire cathode is described. A uniform discharge for laser excitation is obtained. The device produces a CW output of 6 kW. 相似文献
53.
Dynamic properties of bubble domains at low drive pulse field are examined by the bubble transport method. Important findings are as follows. 1) The bubble does not move unless the pulse duration exceeds a critical value which depends on the pulse amplitude. 2) A minimum pulse amplitude is also required for the bubble translation which depends on the pulse duration. 3) As the pulse duration goes to infinity, the minimum drive field approaches a constant value which is different from the dynamic coercivity. 4) As soon as the pulse duration exceeds the critical value, the bubble is displaced discontinuously by a finite distance independent of the drive field. All of these properties are adequately explained by a simple phenomenological theory, in which the domain wall is assumed to be connected by springs to pinning sites until the wall is displaced by a finite distance. 相似文献
54.
Hisamoto H Shimizu Y Uchiyama K Tokeshi M Kikutani Y Hibara A Kitamori T 《Analytical chemistry》2003,75(2):350-354
Here we report a design and synthesis of a chemically functional polymer membrane by an interfacial polycondensation reaction and multilayer flow inside a microchannel. Single and parallel dual-membrane structures are successfully prepared by using organic/aqueous two-layer flow and organic/aqueous/organic three-layer flow inside the microchannel followed by an interfacial polycondensation reaction. By using the inner-channel membrane, permeation of ammonia species through the inner-channel membrane is successfully achieved. Furthermore, horseradish peroxidase is immobilized on one side of the membrane surface to integrate the chemical transform function onto the inner-channel membrane. Here substrate permeation through the membrane and subsequent chemical transformation at the membrane surface are realized. The polymer membrane prepared inside the microchannel has an important role in ensuring stable contact of different phases such as gas/liquid or liquid/ liquid and the permeation of chemical species through the membrane. Furthermore, membrane surface modification chemistry allows chemical transformation of permeated chemical species. These methods are expected to lead to development of complicated and sophisticated chemical systems involving membrane permeation and chemical reactions. 相似文献
55.
During the course of our studies of the development of fluorogenic reagents having a 4,7-disubstituted benzofurazan structure, we previously proposed 7-acetylamino-4-mercapto-2,1,3-benzoxadiazole (AABD-SH) as a fluorogenic reagent for carboxylic acids. Since then, progress has made it possible to estimate the fluorescence quantum yields of the 4,7-disubstituted benzofurazan compounds on the basis of the PM3 calculation of their S1-T2 energies. Subsequently, a new fluorogenic reagent, 4-mercapto-7-methylthio-2,1,3-benzoxadiazole (MTBDSH) was designed and synthesized. In the presence of condensation reagents, triphenylphosphine (TPP) and 2,2'-dipyridyl disulfide (DPDS), MTBD-SH readily reacted with n-caprylic acid within 1 min at room temperature. The derivatives of five carboxylic acids (n-caprylic acid, n-capric acid, lauric acid, myristic acid, and palmitic acid) were well-separated on a reversed-phase column and were fluorimetrically detected at 519 nm with excitation at 391 nm. The detection limits (S/N = 3) were 2.4-5.0 fmol. Thus, MTBD-SH had properties that were considered to be superior. For carboxylic acids, itwas superior not only to AABD-SH, but also to many other conventional reagents. The superiority was examined in terms of its reactivity and sensitivity and the avoidance of interfering peaks that were derived from the reagent itself or degradation products in the chromatogram. 相似文献
56.
In this study, we design a learning environment that supports reflective activities for information seeking on the Web and evaluate its educational effects. The features of this design are: (1) to visualize the learners’ search processes as described, based on a cognitive schema, (2) to support two types of reflective activities, such as “reflection-in-action” and “reflection-on-action”, and (3) to facilitate reflective activities by comparing their own search processes to other learners’ search processes. We have conducted an experiment to investigate the effects of our design. The experimental results confirm that: (1) the participants’ search performance in the instructional group supported by our instructional design improved effectively than in the control group; (2) they changed their ideas about important activities when seeking information on the Web, and (3) they activated their search cycles more than the control group did. 相似文献
57.
Yusuke Kusuda Kinya Fukuda Masao Matsumura Kazuhisa Hagisawa Gaku Okamoto Tatsuo Nakanishi Yoshiyuki Inoue 《Electrical Engineering in Japan》2007,159(4):18-26
Recently, composite insulators have been increasingly employed mainly for economic reasons. We have developed a new type of outdoor termination using a composite insulator, which can be installed horizontally on a steel tower in order to reduce the construction cost. In this outdoor termination, SF6 gas is filled in the composite insulator and a cold shrinkable premolded rubber unit is applied instead of the combined use of a rubber‐molded stress relief cone, epoxy resin insulator and spring unit. The application of the composite insulator, SF6 gas and cold shrinkable premolded rubber unit reduces the total weight and makes it possible to install the termination horizontally on the tower. The new‐type outdoor termination for 77‐kV XLPE cable has already been applied in commercial use and enabled a reduction of the construction costs for power transmission lines. A 154‐kV new‐type outdoor termination has been developed and its initial electrical tests were successfully completed. This paper describes the design and performance of both 77‐kV and 154‐kV new‐type outdoor termination, and a follow‐up survey of the 77‐kV new termination in a commercial use. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 18– 26, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20511 相似文献
58.
Lithium-doped sulfated-zirconia catalysts for oxidative coupling of methane to give ethylene and ethane 总被引:1,自引:0,他引:1
Li-doped sulfated-zirconia catalysts were found to be effective for oxidative coupling of methane (OCM). The catalyst performances depend on the sulfate content and calcination temperature. A maximum C2 yield is attained over the catalysts, which contain 6 wt.% sulfate and calcined at 923–973 K, being closely related to the preparation conditions of sulfated-ZrO2 as solid super-acids. When the performances of the Li-doped sulfated-ZrO2 (Li/SZ) catalysts were tested at 1023 K as a function of reaction time, both the C2 and COx selectivities remained constant over the range of 8 h, but the CH4 conversion decreased from 17.5% to 11.9%. The nature of Li/SZ catalysts for the OCM was investigated by X-ray diffraction, XPS, and NH3 and CO2 TPD measurements. It could be postulated that the sulfated-ZrO2 surface could play an important role in the formation of a catalytically active structure by Li-doping. 相似文献
59.
Masashi Takahashi Shin-Ichi Goto Kazuhisa Mori Izumi Mataga 《Frontiers of Materials Science in China》2008,2(4):437-440
The purpose of this study is to clarify the difference of histology and elemental composition of the cervical enamels among
the human permanent teeth. The reground surfaces at the cervical enamels of them were observed under scanning electron microscopy
(SEM). The contents of seven elements were analyzed quantitatively with electron probe microanalyzer (EPMA). The widths of
the rod sections at the cervical enamels were larger than those at the cuspal enamels. The rod sections at the mesial cervical
enamels in the incisors were more obscure and more decayed by acid solution than those in the premolars and molars. The calcium
and phosphorus contents of the cervical enamels were significantly lower than those of the cuspal enamels. The carbon content
of the cervical enamels was significantly higher than that of the cuspal enamels. The calcium and phosphorus contents of the
cervical enamels were the significantly highest in the premolars. The carbon and sodium contents of the cervical enamels were
significantly highest in the premolars. It is thought that the calcification level is lower, while the content of organic
matter is higher at the cervical enamels than those at the cuspal enamels. It is considered that the sodium causes high calcification. 相似文献
60.