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991.
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993.
论述了金银冶炼产出的氧化渣中,采用单独还原熔炼和粗铋精炼回收铋及其技术控制。阐述了生产实践中的不断摸索和技术改进,介绍了适应以金银熔炼中产出氧化渣为原料,经济地生产市场急需、用户满意的高纯铋的工艺方法。 相似文献
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996.
Certain lowland streams have experienced prehistorical and historical cycles of aggradation, occlusion, degradation, headward incision, and renewed aggradation. Historical cycles appear to be related to human activities. A case study is presented of the Yalobusha River in Mississippi with emphasis on the effects of blockage and removal on aquatic habitats and fish. The adjacent Skuna River, which was channelized and unblocked, was used in space for time substitution to infer effects of blockage removal on the Yalobusha. Variables describing physical aquatic habitat and fish were sampled from three groups of river reaches: unblocked channelized, channelized and blocked, and naturally sinuous. Fish collections were used to compute six indicators of ecological integrity. At baseflow, mean water depths were an order of magnitude lower in the unblocked channelized stream than for the others. In‐channel aquatic habitat volume per unit valley length was 5, 85, and 283 m3/m for the channelized, blocked channelized, and natural reaches, respectively. Mean values for all six ecological indicators were lowest for the channelized group. Species richness was greatest for the channelized blocked reach. The ecological indicators displayed gradients in response to the range of observed physical conditions. Management of corridors susceptible to the cycle described above should involve a blend of measures designed to conserve higher quality habitats. 相似文献
997.
Larisa Glatman Vladimir Drabkin Alexander Gelman 《Journal of the science of food and agriculture》2000,80(3):375-380
Lactic acid bacteria‐induced fermentation of fish was tested with the purpose of developing a novel fish food product with desired meat properties. Three selected lactic acid bacteria strains, isolated from lightly preserved fish products, were inoculated into minced frozen fillet of yellowfin tuna, and changes in fish properties were observed during 52 days of storage at 8 °C. Organoleptic, bacteriological and biochemical studies (pH, histamine, TVB‐N, malonaldehyde) and shelf‐life measurements suggest that Leuconostoc mesenteroides could be considered as a possible starter culture for fish fermentation, but additional experiments should be performed. © 2000 Society of Chemical Industry 相似文献
998.
Martine Morzel Mary M Heapes William J Reville Elke K Arendt 《Journal of the science of food and agriculture》2000,80(11):1691-1697
The effect of a controlled lactic fermentation on textural and ultrastructural properties of salmon fillets was evaluated. When compared with a non‐inoculated cured sample, fermented salmon had unique textural properties since it exhibited significantly higher force (p < 0.05) and work (p < 0.001) values in a penetration test on two sampling days but a consistently lower hardness (p < 0.05) in a Texture Profile Analysis (TPA) rheological test. Study of the myofibrillar ultrastructure showed that basic structures were drastically damaged during processing and storage of fermented and cured salmon. Nevertheless, Z‐lines were better preserved in fermented samples. It is suggested that the slight protective effect of lactic fermentation with the starter L sake may be the consequence of a lower pH, by putatively inhibiting neutral or alkaline proteolytic enzymes. © 2000 Society of Chemical Industry 相似文献
999.
目的对云南省5个淡水湖泊中鱼虾体内的多氯联苯(polychorinated biphenyl,PCBs)污染水平进行调查研究。方法采用气相色谱-质谱联用仪进行检测分析,根据检测结果对云南省淡水湖泊中的鱼虾体内多氯联苯的含量进行食用安全性评估。结果云南省淡水湖泊中鱼虾体内的多氯联苯检出率为90%,多氯联苯的含量范围为ND~1.16μg/kg,平均含量为0.27μg/kg,低于国家标准限量。云南省淡水湖泊中鱼虾体内的多氯联苯按照世界卫生组织(World Health Organization,WHO)规定的多氯联苯毒性当量(toxic equivalent quantity,TEQ)分布于ND~6.51×10~(-5)μg/kg,平均值为1.21×10~(-5)μg/kg,低于欧盟的行动标准限量。结论云南省居民从云南省淡水湖泊鱼虾体内摄入持久性有机污染物多氯联苯的剂量较低,引起的健康风险较低。 相似文献
1000.
由物性分析可知,煤化工石脑油中易裂解的链烷烃含量高(90%(w)),环烷烃、芳烃含量较低,芳烃潜含量低;结合860~900℃下裂解气/液相产物收率对比可知,煤化工石脑油为优质裂解原料,适宜在高温(900℃)下进行裂解;随着裂解温度升高,裂解液相收率降低,液相中芳烃含量提高,裂解液相以C_5~205℃组分为主(75%(w)),苯、甲苯、二甲苯合计占70%(w)以上。与炼厂拔头油、石脑油相比,煤化工石脑油价格低、产量将逐年增加,裂解乙烯、三烯收率高而液相产物收率略低,因此,煤化工石脑油作为乙烯企业原料结构的合理补充,将是解决乙烯原料短缺和提升煤炭资源深加工经济效益的新路径。 相似文献