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541.
Gross alpha and gross beta activities were determined for 27 different tap water samples collected from Eastern Black Sea region of Turkey. The instrumentation used to count the gross alpha and gross beta activities was a alpha/beta counter of the low background multiple detector type with 10 sample detectors (Berthold LB770). The obtained results showed that natural activity concentrations of alpha- and beta-emitting radionuclides in tap water samples did not exceed WHO and ITS recommended levels. Concentrations ranging from 0.2 mBq/l to 15 mBq/l and from 25.2 mBq/l to 264.4 mBq/l were observed for the gross alpha and gross beta activities, respectively. For all samples the gross beta activities were higher than the corresponding gross alpha activities. 相似文献
542.
Use of Neural Net Models to Forecast Atmospheric Pollution 总被引:1,自引:0,他引:1
The forecast of the CO and NO2 concentration levels has been obtained by the 3-layer Perceptron Neural Network with Error Backpropagation learning rule.This study shows the 3-layer Perceptron performances in relationship with the choice of the activation functions parameters (depending on the statistical values of the input/output variables).A first simulation set using data at 1 hour before has been utilized to forecast CO levels. A second simulation set with data at 12–24 hours before has been used to forecast NO2 levels.The Neural Net's performance appears to be very good both for the parameters activation function optimisation and the variables choice. 相似文献
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An excess of structural anomalies is observed in twins compared to singletons. Approximately 1–2% of twin pregnancies may face the dilemma of expectant management versus selective termination following diagnosis of an anomaly affecting only one fetus. If the option of selective fetocide is considered, the main variable determining the technique to achieve this aim is chorionicity. In a dichorionic pregnancy, passage of substances from one twin into the circulation of the co-twin is unlikely due to the lack of placental anastomoses, hence KCl can be injected safely into the circulation of the affected twin to produce fetal asystole. In monochorionic twin pregnancies, selective termination needs to be performed by ensuring complete and permanent occlusion of both the arterial and venous flows in the umbilical cord of the affected twin, in order to avoid acute haemorrhage from the co-twin into the dying fetus, which may lead to death or organ damage. Bipolar cord coagulation under ultrasound guidance is associated with approximately 70–80% survival rates. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
549.
Sylvia Wanner Lang Patricia F. Waller Jean Thatcher Shope 《Journal of Safety Research》1996,27(4):241-257
The high motor-vehicle crash rate of young drivers may be attributed to both driving inexperience and a greater tendency to engage in risk-taking behavior. This study examines risk-taking behavior, as indicated by single-vehicle crashes and injury crashes, and factors associated with these behaviors, based on measures of demographic, psychosocial, and substance use obtained from high school senior questionnaires. Because previous work indicated different predictors for young men and young women, separate logistic regression analyses were conducted. For young women, propensity toward cigarette use was associated with higher rates of single-vehicle crashes; while race, alcohol misuse, and friends' involvement with alcohol and marijuana were associated with injury crashes. For young men, availability of substances, driving frequency, alcohol misuse, and propensity toward marijuana use were associated with higher rates of single-vehicle crashes. Young men's living situation, availability of substances, and marijuana use were related to injury crashes. 相似文献
550.
次氯酸钠氧化预处理草甘膦生产废水 总被引:6,自引:0,他引:6
利用次氯酸钠对草甘膦生产废水进行预处理,废水pH对处理效果影响不大,可将次氯酸钠直接投入到原碱性废水中,在其用量相当理论量的40%、氧化时间为4h时,草甘膦的去除率为98%。预处理后的废水对厌氧消化过程不再产生抑制作用。 相似文献