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A. Sciarrone B. Masturzo G. Botta S. Bastonero M. Campogrande E. Viora 《黑龙江环境通报》2005,25(12):1129-1132
Prevalence of congenital heart disease increases with nuchal translucency (NT) thickness. First-trimester fetal bradycardia may result from heart block associated with complex congenital heart disease. We report two cases detected in the first trimester of pregnancy, in which both fetuses showed an increased nuchal translucency and bradycardia. Fetal karyotype was normal in both fetuses. First-trimester fetal echocardiography was performed and, in both cases, complex congenital heart disease was diagnosed. We discuss the added role of fetal heart rate in first-trimester ultrasound screening, in fetuses with increased nuchal translucency and normal karyotype. We stress, as well, the importance of echocardiography performed in the first trimester as a potential tool for early diagnosis in selected cases. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Prior research has demonstrated the utility of metrics based on spatial velocity gradients to characterize and describe stream
habitat, with higher gradients generally indicative of higher levels of physical heterogeneity and thus habitat quality. However,
detailed velocity data needed to compute these metrics are difficult to obtain. Acoustic Doppler current profilers (ADCP)
may be used to rapidly collect detailed representations of river velocity fields. Herein we demonstrate use of ADCP to obtain
ecologically relevant data and compute associated metrics. Data were collected from four reaches of the Little Tallahatchie
River in northern Mississippi. Sampled reaches were selected to observe velocity regimes associated with three distinctly
different conditions: downstream from a major flow obstruction (a low weir), downstream from the apices of each of two bends,
and within an extremely long, straight reach created by channelization. Three-dimensional velocity data sets from each site
were used to compute metrics of habitat quality proposed by others. A habitat metric based on the presence of rotational flow
in the vertical plane proved to be the best discriminator among conditions within the sampled reaches. Two of four habitat
quality metrics computed from these measured velocities were greatest for the sharpest meander bend. ADCP hold great potential
for study of riverine physical aquatic habitats, particularly at the reach scale. Additional work is needed to develop generally
applicable field protocols and data reduction tools. Specifically, guidelines for ADCP settings and configuration appropriate
for a range of riverine site conditions must be developed. Advances in instrumentation are needed to allow collection of information
in closer proximity to the free surface and solid boundaries. 相似文献
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METEOR 360AC型多普勒雷达功能和风场反演UW技术简介 总被引:3,自引:0,他引:3
介绍了民航华东空中交通管理局气象中心引进的Gematronik公司多普勒天气雷达的主要产品及功能,并着重介绍了一种实用的单多普勒雷达0风场反演方法-UW(均匀风)技术。 相似文献
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采用声学多普勒测速仪(ADV)对水下推动器运行时氧化沟流场进行分析,结果表明:水下推动器单独运行时氧化沟直道流速分布规律与曝气转盘单独运行时不同,靠近叶轮处流速分布沿水深与沟宽都不同,可看作是一个点射流与典型明渠流动混合的流动,具有明显的三维性。通过一段距离的流速掺混,沟内液流可达到一个准二维流动。水下推动器安装在断面中部时的断面平均流速比安装在底部时大18%左右,动力利用率高,较有效地起到推流作用;安装在断面中部时紊动强度分布稳定时的断面离叶轮迎水面的相对距离比安装在断面底部短。 相似文献
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