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991.
Yifat Ochshorn Michael J. Kupferminc Igal Wolman Avi Orr-Urtreger Ariel J. Jaffa Yuval Yaron 《黑龙江环境通报》2001,21(7):547-549
Combined first trimester screening using pregnancy associated plasma protein-A (PAPP-A), free β-human chorionic gonadotrophin, and nuchal translucency (NT), is currently accepted as probably the best combination for the detection of Down syndrome (DS). Current first trimester algorithms provide computed risks only for DS. However, low PAPP-A is also associated with other chromosome anomalies such as trisomy 13, 18, and sex chromosome aneuploidy. Thus, using currently available algorithms, some chromosome anomalies may not be detected. The purpose of the present study was to establish a low-end cut-off value for PAPP-A that would increase the detection rates for non-DS chromosome anomalies. The study included 1408 patients who underwent combined first trimester screening. To determine a low-end cut-off value for PAPP-A, a Receiver–Operator Characteristic (ROC) curve analysis was performed. In the entire study group there were 18 cases of chromosome anomalies (trisomy 21, 13, 18, sex chromosome anomalies), 14 of which were among screen-positive patients, a detection rate of 77.7% for all chromosome anomalies (95% CI: 55.7–99.7%). ROC curve analysis detected a statistically significant cut-off for PAPP-A at 0.25 MoM. If the definition of screen-positive were to also include patients with PAPP-A<0.25 MoM, the detection rate would increase to 88.8% for all chromosome anomalies (95% CI: 71.6–106%). This low cut-off value may be used until specific algorithms are implemented for non-Down syndrome aneuploidy. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
992.
T.W.A. Whitfield 《Journal of environmental psychology》1983,3(3):221-237
The work reported compared the predictive ability of two theories of aesthetic behaviour, using normal, everyday objects. This involved utilizing simulated items of furniture in three experiments in which predictions deduced from the ‘collative-motivation’ model and what has been termed a ‘preference-for-prototypes’ model were made to compete empirically. For each of the five pairs of discrepant expectations formulated in the three experiments the outcomes were inconsistent with Berlyne's model, while supporting the prototypicality model. A number of theoretical implications are drawn from these findings. 相似文献
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996.
大气污染对悬铃木叶绿素及抗氧化酶系的影响 总被引:6,自引:0,他引:6
大气污染会影响悬铃木叶片内叶绿素含量以及活性氧清除系统,致使植物体内叶绿素含量降低,抗氧化酶系统活性上升,并使植物体内丙二醛积累增加。交通污染对植物的影响程度与工业污染相当,应引起重视。绿化可减少空气污染,提高环境质量。 相似文献
997.
Ken T Hepburn HR Radloff SE Yusheng Y Yiqiu L Danyin Z Neumann P 《Die Naturwissenschaften》2005,92(10):492-495
Defensiveness of honeybee colonies of Apis cerana and Apis mellifera (actively balling the wasps but reduction of foraging) against predatory wasps, Vespa velutina, and false wasps was assessed. There were significantly more worker bees in balls of the former than latter. Core temperatures
in a ball around a live wasp of A. cerana were significantly higher than those of A. mellifera, and also significantly more when exposed to false wasps. Core temperatures of bee balls exposed to false wasps were significantly
lower than those exposed to V. velutina for both A. cerana and for A. mellifera. The lethal thermal limits for V. velutina, A. cerana and A. mellifera were significantly different, so that both species of honeybees have a thermal safety factor in heat-killing such wasp predators.
During wasps attacks at the hives measured at 3, 6 and 12 min, the numbers of Apis cerana cerana and Apis cerana indica bees continuing to forage were significantly reduced with increased wasp attack time. Tropical lowland A. c. indica reduced foraging rates significantly more than the highland A. c. cerana bees; but, there was no significant effect on foraging by A. mellifera. The latency to recovery of honeybee foraging was significantly greater the longer the duration of wasp attacks. The results
show remarkable thermal fine-tuning in a co-evolving predator–prey relationship. 相似文献
998.
活性污泥二次污染问题的探讨 总被引:2,自引:0,他引:2
讨论了城市污水分别经过混凝沉降和A/O工艺处理后,将所产生的污泥分别用甲苯萃取,采用GC/MS测定了两种样品中的有机化合物含量。结果表明,在A/O工艺处理城市污水过程中,活性污泥的吸附作用是主要的,降解作用是次要的;与原活性污泥相比较,A/O工艺排放的活性污泥是一种更加危险的二次污染物。 相似文献
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1000.
Many estuarine and coastal planktonic copepods depend on the hatching of benthic resting eggs for recruitment ofnauplii to the water column population. The potential effects of two organochlorine pesticides, hexchloriobinzene (HCH) and dichlorodiphenyltrichloroethane (DDT), on the recruitment of A ccu'tla pacifica nauplii from benthic resting eggs in the seabed of Xiamen Bay were experimentally investigated. The abundance of A. pacifica nauplii hatched from the sediment significantly decreased with the increase of pesticide concentration. Trimmed Spearman-Karber analysis gave sediment 96-h LC50 values were 84.81 ng/g for HCH, and 157.94 ng/g for DDT. The median AI (Al50) was -0.77, which suggested that the combined effect of riCH and DDT showed a weak effect than individual effects. There was a positive relationship between mortality and exposure time in DDT treatment, while the relationship was not significant in HCH treatment. The results suggest that organochlorine pesticides can reduce recruitment of A. pacifica nauplii from benthic resting eggs to planktonic population. 相似文献