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151.
Boris M. Epelbaum Kiyoshi Shimamura Satoshi Uda Junichi Kon Tsuguo Fukuda 《Crystal Research and Technology》1996,31(8):1077-1084
The μ-PD method originally developed for oxide crystals has been modified and applied for filamentary silicon crystal growth. Our main modification of μ-PD method is concerned with an arrangement of melt permeable feeder which is inserted into the nozzle. The feeder finishes by a sharp tip the diameter of which (is almost the same as that of the desired semiconductor fiber, i.e., less than 150 μm. Silicon fibers were grown from the small liquid pool at the end of the feeder. Three types of crucible-die arrangement were designed and tested. The best results were obtained with the help of inclined insert made of graphite fibers because of its ability to quench oscillations and longer operation life. Fiber crystals, 100 μm in diameter and 70 mm in length, have been grown successfully. Small meniscus stability, operating limits of μ-PD method and silicon carbide formation during the growth process are discussed. 相似文献
152.
Motomasa Kobayashi Nobuyoshi Shimizu Isao Kitagawa Yoshimasa Kyogoku Nobuyuki Harada Hisashi Uda 《Tetrahedron letters》1985,26(32):3833-3836
The absolute stereostructures of two pentacyclic hydroquinones, halenaguinol () and halenaquinol sulfate () from the Okinawan marine sponge Xestospongia sapra, have been determined by means of theoretical calculation of CD spectra. 相似文献
153.
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156.
Yoshitaka Takezawa Noriaki Taketani Seikichi Tanno Shuichi Ohara 《Journal of Polymer Science.Polymer Physics》1992,30(8):879-885
We have studied simple empirical equations to estimate light absorption loss αv due to harmonics of molecular vibrations of transparent amorphous polymers used in plastic optical fibers (POFs). In the visible region, absorption involves two losses. One is αv, and the other is the electronic transition absorption loss, αe. Of the two, αv is considerably larger than αe in the wavelength region used for optical communication with POFs. We have clarified relationships between chemical structure of repeat units of polymers and αv. We find that αv is proportional to the concentration of specific chemical bonds (C? H, N? H, and Obond;H bonds) in the polymer solid, and we propose empirical equations to estimate αv from the polymer density and the chemical structure of the repeat unit. These equations are used to estimate αv of several polymers [i.e., poly(methyl methacrylate), polystyrene, and polycarbonate]. The estimated values are nearly equal to the experimental or reference values. Furthermore, to minimize the attenuation in the POF, we conclude that the POF core polymer should have no N? H, O? H, or aliphatic C? H bonds in its repeat unit. 相似文献
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158.
For the p-th cyclotomic field k, Iwasawa proved that p does not divide the class number of its maximal real subfield if and only if the odd part of the group of local units coincides
with its subgroup generated by Jacobi sums related to k. We refine and give a quantitative version of this result for more general imaginary abelian fields. Our result is an analogy
of the famous result on “semi-local units modulo cyclotomic units”.
Received: 2 May 1997 / Revised version: 11 November 1997 相似文献
159.
During the electrophoresis separation of B- and T-cells from lymphocytes employing a microcapillary chip, they were found to become inactive in the reservoir after a short time. This was caused by the buffer solution becoming alkaline due to electrolysis. This was considered to take place in chips with small reservoir volumes. The pH change was confirmed by the ISFET (ion-sensitive field effect transistor) embedded in the chip. To suppress the pH change, two methods were studied. One is the insertion of a salt bridge just in front of and behind the capillary, thus introducing an electric potential but stopping flow of the acid and alkaline solutions into the capillary. The other is neutralization of the alkaline solution in the reservoir by injecting the acid solution produced in another capillary with the same structure by employing an electroosmotic flow (EOF) pump. Both methods achieved no pH change during electrophoresis measurements in the microcapillary. 相似文献
160.
Toshinobu?TokumotoEmail author Ayami?Kondo Junko?Miwa Ryo?Horiguchi Mika?Tokumoto Yoshitaka?Nagahama Noriyuki?Okida Katsutoshi?Ishikawa 《BMC biochemistry》2003,4(1):6