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镁合金压铸实践
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作者 杨建荣 喻德 《铸造工程.造型材料》 2003年第3期24-26,共3页
由于镁合金材料的易燃性和激冷性(材料结晶温度范围短),导致镁合金压铸在我国还处于初步发展阶段.通过采用科学合理的熔化、压铸工艺,可以解决镁合金由于材料本身所决定的压铸问题,本文对压铸工艺的编排做了较为详细的介绍.
关键词 镁合金 压力铸造 熔化 易燃性 激冷性 铸造工艺
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Antioxidation and ATPase activity in the gill of mud crab Scylla serrata under cold stress
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作者 孔祥会 王桂忠 李少菁 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2007年第2期221-226,共6页
Mud crab (Scylla serrata) is an important commercial crustacean in China. An experiment was designed to study the effect of cold stress on S. serrata. After a one-week adaptation at 28℃, the temperature is suddenly... Mud crab (Scylla serrata) is an important commercial crustacean in China. An experiment was designed to study the effect of cold stress on S. serrata. After a one-week adaptation at 28℃, the temperature is suddenly reduced to 4℃. The crabs were sampled every 2 h for 10 h and dissected immediately to measure the enzyme activity. The crabs at room temperature (28℃) were used as the control group. The activity of superoxide dismutase (SOD), catalase (CAT) and gkttathione peroxidase (GPX), the content of malondialdehyde (MDA) and the activity of 4 ATPases (Na^+, K^+-ATPase, Mg^2+-ATPase; Ca^2+-ATPase; Ca^2+, Mg^2+-ATPase) were measured biochemically. In contrast to the control group, the SOD activity increased significantly from 2 to 6 h after the cold stress, and then decreased. The CAT and GPX activities increased in 2 h, and then decreased gradually. The content of MDA increased gradually in 4 h. The activity of Na^+, K^+-ATPase decreased in 2 h, increased up to the top value at Hour 6, then decreased again. The activities of Mg^2+-ATPase, Ca^2+-ATPase and Ca^2+, Mg^2+-ATPase increased significantly in 6 h, insignificantly in any other hours. Under cold stress, the activity of antioxidative enzymes in S, serrata was reduced at first then stabilized, ROS-scavenging weakened, and MDA accumulated gradually in the gill after 6 h. The activity of the 4 ATPases in the crab decreased after 6 h, suggesting that the ability to regulate ion concentration has been paralyzed. Therefore, the maximum period to sustain healthy meat in the crab under cold stress is 6 hours. 展开更多
关键词 ANTIOXIDATION ATPase gill cold stress Scylla serrata
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