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991.
992.
Chia-Hsun Tu Yi-Sheng Lai Dim-Lee Kwong 《Electron Device Letters, IEEE》2006,27(5):354-356
This letter investigated the reproducible bistable resistance switching characteristics of a single-layer organic device based on 8-hydroquinoline aluminum (Alq3) fabricated by spin coating. By controlling the ON-state current through the Alq3 films, it has been possible to achieve various resistance states of the films. In addition, the resistance of the ON-state Alq3 films also affects the threshold current and voltage to switch off the device. The independence of the current-injected direction to erase the ON state implies that the filament theory could elucidate the observed phenomenon. The ratio between low- and high-resistance states can reach five orders of magnitude, which will be a potential material for nonvolatile memory application. 相似文献
993.
P Verdier-Pinard JY Lai HD Yoo J Yu B Marquez DG Nagle M Nambu JD White JR Falck WH Gerwick BW Day E Hamel 《Canadian Metallurgical Quarterly》1998,53(1):62-76
Originally purified as a major lipid component of a strain of the cyanobacterium Lyngbya majuscula isolated in Cura?ao, curacin A is a potent inhibitor of cell growth and mitosis, binding rapidly and tightly at the colchicine site of tubulin. Because its molecular structure differs so greatly from that of colchicine and other colchicine site inhibitors, we prepared a series of curacin A analogs to determine the important structural features of the molecule. These modifications include reduction and E-to-Z transitions of the olefinic bonds in the 14-carbon side chain of the molecule; disruption of and configurational changes in the cyclopropyl moiety; disruption, oxidation, and configurational reversal in the thiazoline moiety; configurational reversal and substituent modifications at C13; and demethylation at C10. Inhibitory effects on tubulin assembly, the binding of colchicine to tubulin, and the growth of MCF-7 human breast carcinoma cells were examined. The most important portions of curacin A required for its interaction with tubulin seem to be the thiazoline ring and the side chain at least through C4, the portion of the side chain including the C9-C10 olefinic bond, and the C10 methyl group. Only two modifications totally eliminated the tubulin-drug interaction. The inactive compounds were a segment containing most of the side chain, including its two substituents, and analogs in which the methyl group at the C13 oxygen atom was replaced by a benzoate residue. Antiproliferative activity comparable with that observed with curacin A was only reproduced in compounds that were potent inhibitors of the binding of colchicine to tubulin. Molecular modeling and quantitative structure-activity relationship studies demonstrated that most active analogs overlapped extensively with curacin A but failed to provide an explanation for the apparent structural analogy between curacin A and colchicine. 相似文献
994.
A discrete replacement model for a repairable system which is subject to shocks and minimal repairs is discussed. Such shocks can be classified, depending on its effect to the system, into two types: Type I and Type II shocks. Whenever a type II shock occurs causes the system to go into failure, such a failure is called type II failure and can be corrected by a minimal repair. A type I shock does damage to the system in the sense that it increases the failure rate by a certain amount and the failure rate also increases with age due to aging process without external shocks; furthermore, the failure occurred in this condition is called type I failure. The system is replaced at the time of the first type I failure or the n-th type Il failure, whichever occurs first. Introducing costs due to replacement and mininal repairs, the long-run expected cost per unit time is derived as a criterion of optimality and the optimal number n∗ found by minimizing that cost. It is shown that, under certain conditions, there exists a finite and unique optimal number n∗. 相似文献
995.
996.
997.
介绍了灯饰横梁零件成形工作过程及工艺过程,对灯饰横梁零件压形整形复合模作了较详细介绍,对生产类似产品的厂家有一定的参考应用价值。 相似文献
998.
制备出以混合氧化物为载体的固载杂多酸盐催化剂TiSiW1 2 O4 0 /TiO2 -SnO2 ,以油酸和正丁醇为原料 ,系统研究了催化合成油酸丁酯的影响因素 ,确定了该反应的优化条件 :醇酸摩尔比为 2∶1,催化剂用量为反应物总质量的 1 5 % ,反应时间 60min ,反应温度 13 0~ 14 0℃。在此反应条件下 ,油酸丁酯的收率达到 90 8%。 相似文献
999.
1000.
Lih-Gen Sheu Kai-Ping Chuang Y. Lai 《Photonics Technology Letters, IEEE》2003,15(7):939-941
We theoretically demonstrate that a high-quality fiber Bragg grating dispersion compensator can be fabricated by a properly designed single-period overlap-step-scan exposure method. A practical design example and a detailed tolerance analysis of this new fabrication method are given. 相似文献