Prenatal diagnosis of neurofibromatosis type 1: From flanking rflps to intragenic microsatellite markers

Even though the neurofibromatosis type 1 (NF1) gene was cloned more than 3 years ago, the process of identifying mutations has not been fruitful, and genetic counselling is mainly based on the use of linked markers. Since 1990, we have analysed 130 NF1 families and have performed six prenatal diagnoses. In each case, genetic counselling has relied on linked markers and informativity was achieved in all of them. The use of intragenic microsatellite polymorphisms (IVS27AAAT2.1, IVS27AC28.4, IVS27AC33.1, and IVS38GT53.0) has increased the informativeness in our series of NF1 families to an average of 90 per cent, providing accurate diagnosis and confirmation of the disease status.     

Prenatal diagnosis of chondroectodermal dysplasia with fetoscopy

Chondroectodermal dysplasia (Ellis-van Creveld syndrome) has previously been diagnosed prenatally only once, using fetoscopy. We report on two consecutive pregnancies in a woman at risk of having a child with the syndrome during which fetoscopic visualization was performed. Ellis-van Creveld syndrome was diagnosed prenatally in one instance, while it could be excluded in the other one. Non-invasive prenatal diagnosis of the syndrome is discussed.     

First-trimester prenatal diagnosis of Sanfilippo C disease

At 10 weeks' gestation, chorionic villus biopsy was obtained from a woman at risk for Sanfilippo type C disease. Acetyl-CoA: α-glucosaminide N-acetyltransferase activity was markedly deficient. The pregnancy was terminated at 12 weeks' gestation and follow-up study on fetal fibroblasts confirmed the diagnosis.     

Prenatal diagnosis of cleft lip and palate by ultrasound

Bilateral cleft lip and cleft palate can be diagnosed by ultrasonography prior to 20 weeks of pregnancy. The anomaly produces an abnormal facial profile and, on cross-section, the clefts in the maxilla are demonstrable. The method is illustrated by sonograms from a fetus in which the defect was diagnosed before trisomy 13 became known by karyotyping.     

基于时频分析的裂纹转子碰摩故障特征研究

为研究转子系统耦合故障特性,采用有限元方法建立了含有横向裂纹、转静碰摩的非线性转子动力学模型。首先研究了不同转速下裂纹、碰摩单一故障下转子系统的振动响应,其次研究了两种故障耦合情况下系统的振动响应特征。采用波形图、FFT谱图、瞬时频率和Hilbert-Huang时频谱(HHS)相结合的方法对故障转子振动信号进行了分析。分析结果表明:运用多种时频分析相结合的方法可以较为全面地了解转子的故障特征,裂纹转子在1/5、1/3临界转速时会发生较为明显的5X、3X谐波,且裂纹的产生会导致响应幅值增大,从而引起更为严重的碰摩。      

A juvenile lizard specimen with well-preserved skin impressions from the Upper Jurassic/Lower Cretaceous of Daohugou, Inner Mongolia, China

Lizards are now relatively well known from the Yixian Formation of northeastern China. In this study, we describe a juvenile lizard from a fossil horizon at Daohugou, Inner Mongolia. These beds predate the Yixian Formation, and are probably Late Jurassic or earliest Cretaceous in age. The new specimen thus documents the first lizard material from the Daohugou locality and is the earliest lizard skeleton from China. Comparisons with developmental stages of modern lizards suggest the Daohugou lizard is a hatchling. Although tiny, the specimen is notable in preserving exquisite skin impressions showing the variation in scalation across the body, the shape and position of the cloacal outlet, and details of the manus and pes. These are the earliest recorded lepidosaurian skin traces. In its general proportions and the possession of paired frontals, the small Daohugou lizard resembles both the Yixian taxon Yabeinosaurus tenuis and the questionable Jeholacerta formosa, but it differs from the latter in scalation and, based on other characters, may be distinct from both.     

基于非线性技术锅炉故障分析*

为预测和判断锅炉故障的发生,完善锅炉故障检测技术,基于锅炉运转具有非线性特点,提出将非线性评价指标应用于锅炉故障诊断。研究特征信号的非线性特性,通过确定延迟时间和嵌入维数来重构相空间;采用混沌分形理论研究非线性评价指标;提取最大Lyapunov指数和关联维数,并为收集的每种特征信号选择最合适的非线性指标。结果表明:蒸汽压力的非线性特征指标应选择关联维数,烟气温度1、烟气温度2、水管温度1和水管温度2的非线性特征指标应当选择最大Lyapunov指数。     

航天器在轨自主热故障诊断专家系统研究

航天器在轨自主进行热故障诊断对其顺利完成任务具有非常重要的意义。文中所提出的专家系统推理机制采取基于事例和基于规则相结合的方法构造;而知识获取广泛吸取历史经验和专家知识,采用产生式规则进行知识表示。最后利用VB完成了该专家系统,通过验证,发现它具有很好的实用性。