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1.
The fetal heart rate (FHR) was continuously monitored during 42 umbilical vessel punctures performed at the placental insertion of the cord in 24 diagnostic fetoscopies in which pure fetal blood was obtained. In only one patient did a deceleration first appear during puncture and aspiration of fetal blood. In two patients decelerations preceded fetoscopy and in two others they began during the fetoscopy but before puncture of an umbilical vessel. In 19 patients, the FHR did not change at all during the procedure. Fetal haemorrhage after sampling was either absent or minimal. Six pregnancies were terminated because a positive diagnosis had been made and 18 healthy babies were born. Umbilical cords were examined after 7 terminations of pregnancy and after 6 deliveries. In the former group the puncture could just be seen with the naked eye and the needle track was demonstrated histologically in 6. No traces of the puncture or other abnormalities were found in the cords after delivery. Fetal blood sampling from umbilical cord vessels, particularly at the placental insertion of the cord, is the technique of choice since pure fetal blood can be obtained without increasing the risk of fetoscopy. 相似文献
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通过引入应变速率、损伤变量以及刚度退化指标等参数,建立了应变率相关的混凝土弹塑性损伤模型。运用该模型对某重力坝厂房坝段分别就率相关及率无关两种情况进行了三维非线性地震响应时程分析。深入研究了混凝土应变速率等相关特性对结构动力响应的影响。结果表明,应变速率对混凝土的力学性能有一定的影响,随着应变速率的增加,坝体结构的变形减小,主拉应力有所提高,应变能有所减小以及开裂损伤有一定的降低。所得结论对混凝土重力坝的震害研究有一定的参考价值。 相似文献
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Magdalini Soupioni Kyriaki Vlachou Alexandra Psarologou Argyro Bekatorou 《毒物与环境化学》2016,98(10):1191-1199
AbstractThe extent to which selected ethanol and lactic acid production bioprocesses contribute to whey waste abatement was examined. Alcoholic fermentation of whey was carried out by kefir cells immobilized on grape stalks, delignified cellulosic materials, or brewer's spent grains. Lactic acid fermentation was also performed by free kefir cells with or without addition of brewer's spent grains as promoting material. Since whey fermentation rate is affected by the lactose uptake rate, 14C-labeled lactose was used to study the fermentation ability of kefir. The highest reductions in biochemical oxygen demand and chemical oxygen demand of whey, about 68% and 52%, respectively, were achieved by lactic acid fermentation in 6 h at 37 °C and pH 5.5, in the presence of 120 g brewer's spent grains. Additionally, at the same conditions, the highest 14C-labeled lactose uptake rate by kefir and consequently the highest alcoholic fermentation rate were also recorded. However, greater reductions in biochemical oxygen demand and chemical oxygen demand of whey are required prior to final disposal. 相似文献
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以钠基膨润土为原料,制备了铁镍无机改性土和铁镍有机复合改性土,并应用于造纸废水的处理,探讨了改性土用量、废水pH值、搅拌时间等因素对COD去除率的影响,通过正交实验对实验条件进行了优化.结果表明:铁镍有机复合改性土和铁镍元机改性土对废水的处理效果明显好于原土;膨润土的用量、废水的pH对COD的去除率影响较大;对于铁镍无机改性土,吸附剂用量为12g/L,溶液pH=2,吸附时间为10 min时,对废水中COD的去除率为54.06%;对于铁镍有机复合改性土,吸附剂用量为14g/L,溶液pH=3,吸附时间为20 min时,对废水中COD的去除率为70.10%. 相似文献
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温度及外加碳源对生物脱氮除磷过程的影响 总被引:3,自引:0,他引:3
针对污水处理厂普遍面临的进水碳源不足及冬季低温时出水氮磷不能稳定达标的问题,研究了温度(21、15和10℃)和外加碳源(乙酸)对活性污泥缺氧条件下反硝化及释磷过程的影响。结果表明,在缺氧条件下投加乙酸,释磷与反硝化反应可同时进行,且乙酸投量的增加仅延长快速碳源反硝化阶段及缺氧释磷阶段的反应时间;温度降低为15℃和10℃时,快速碳源反硝化阶段反硝化速率及缺氧释磷速率较21℃分别降低了约29.2%、42.2%和26.1%、32.3%。当硝态氮目标去除量与磷酸盐目标释放量之比超过5时,乙酸的最优投量以满足反硝化要求为准,计算得出21、15和10℃时常州某城镇污水处理厂乙酸最优投加量计算值约为30、39和46 mg/L。 相似文献
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Spalinger SM von Braun MC Petrosyan V von Lindern IH 《Environmental monitoring and assessment》2007,130(1-3):57-72
House dust has been identified as a major exposure medium for lead (Pb) in children. High levels of Pb in soil and house dust
have been recorded at the Bunker Hill Superfund Site (BHSS) in northern Idaho, an historic mining and smelting district. Soil
and dust remediation at the site was required; however, regional background soil and dust Pb levels had not been well characterized.
The objective of this survey was to determine background house dust Pb levels and to compare those levels with concentrations,
and dust and Pb loading rates measured at the BHSS. Soil and house dust samples were collected in five towns demographically
similar to the BHSS but unaffected by the mining industry. The background concentrations and loading rates were significantly
lower than those observed at the site. House age was a significant factor affecting background soil and house dust Pb concentrations
and loading rates. 相似文献
10.
制药废水硝化-反硝化除氮研究 总被引:12,自引:0,他引:12
含高浓度氮的制药废水经好氧生化处理后,虽然出水的COD,BOD5均可达到行业排放标准,但TN仍高达约170mg/L。本研究在曝气池中设置填料,利用生物膜外层好氧,内层缺氧厌氧的条件,使硝化-反硝化脱氮在同一构筑物内进行,NH3-N和TN去除率分别可达约90%和70%。在本试验条件范围内,温度越高,负荷越低,硝化和反硝化作用越完全,NH3-N和TN去除率越高。 相似文献