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111.
钛酸酯催化环氧树脂固化动力学研究 总被引:6,自引:2,他引:4
用FTIR“原位”技术,研究了钛酸酯(Tc-114)偶联剂对环氧E-44和二氨基二苯基甲烷(DDM)固化反应的催化作用,得出固化程度与时间的关系曲线。又根据DSC曲线,分别算出加有Tc-114和不加Tc-114的两个固化体系的反应表观活化能和反应级数。结果表明,Tc-114的存在使环氧固化反应活化能降低,催化作用明显。 相似文献
112.
A 50 year old man presented with sudden abdominal pain, abdominal distension and shock. At emergency laparotomy a large amount of blood was found in the peritoneal cavity. There was micronodular cirrhosis of the liver and the spleen was enlarged. The bleeding was traced to distended veins in the right paracolic gutter which were oversewn and the abdomen closed. A coagulopathy was diagnosed and treatment including high dose aprotinin commenced. However, he continued to bleed and at a second laparotomy the area of previous haemorrhage was packed. Further deterioration continued until death 12 hours later. Intraperitoneal haemorrhage from ectopic varices is a rare occurrence. There is a high mortality rate usually due to an advanced coagulopathy. This is the first report of aprotinin being used in an attempt to treat this. On the basis of this report aprotinin would not seem to be of benefit for this condition. 相似文献
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114.
VNS反应合成LLM-116 总被引:2,自引:0,他引:2
以1,3-二硝基吡唑为原料,经热重排、氨气中和得到3,5-二硝基吡唑铵盐,然后酸化得到3,5-二硝基吡唑。以三甲基肼碘化物(TMHI)作为异常亲核取代氢(VNS)反应试剂,与3,5-二硝基吡唑在叔丁醇钾为催化剂,利用VNS反应合成4-氨基-3,5-二硝基吡唑(LLM-116)。采用红外分析、核磁共振、元素分析等仪器鉴定了其结构,讨论了VNS反应机理及影响因素。通过实验,得出最佳VNS反应试剂为TMHI,反应时间为4h,反应温度为25℃,收率达到60%。 相似文献
115.
Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines
A series of low noble-metal coment monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 (where OSM was oxygen storage material) catalyst with Ce0.5Zr0.5-MnOx(3%MnOx) OSM held low light-off temperature for CO, HC, and NO; quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently comrol exhaust emission of small gasoline engines. 相似文献
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The authors previously reported that American shad (Alosa sapidissima) can detect sounds from 100 Hz to 180 kHz, with two regions of best sensitivity, one from 200 to 800 Hz and the other from 25 to 150 kHz [Mann et al., Nature 389, 341 (1997)]. These results demonstrated ultrasonic hearing by shad, but thresholds at lower frequencies were potentially masked by background noise in the experimental room. In this study, the thresholds of the American shad in a quieter and smaller tank, as well as thresholds for detecting stimulated echolocation sounds of bottlenosed dolphins was determined. Shad had lower thresholds for detection (from 0.2 to 0.8 kHz) in the quieter and smaller tank compared with the previous experiment, with low-frequency background noise but similar thresholds at ultrasonic frequencies. Shad were also able to detect echolocation clicks with a threshold of 171 dB re: 1 microPa peak to peak. If spherical spreading and an absorption coefficient of 0.02 dB/m of dolphin echolocation clicks are assumed, shad should be able to detect echolocating Tursiops truncatus at ranges up to 187 m. The authors propose that ultrasonic hearing evolved in shad in response to selection pressures from echolocating odontocete cetaceans. 相似文献
120.
C Mao R Vig TK Venkatachalam EA Sudbeck FM Uckun 《Canadian Metallurgical Quarterly》1998,8(16):2213-2218