A prospective study of amniotic fluid cholinesterases: Comparison of quantitative and qualitative methods for the detection of open neural tube defects

The value of quantitative and qualitative methods of cholinesterase (ChE) analysis in the detection of open neural tube defect (NTD) has been assessed in a prospective survey of 1495 mid-trimester amniotic fluids. Using a quantitative method the mean ChE values were much lower in fluids from pregnancies of normal outcome but it was not possible to discriminate these fluids completely from those associated with NTD pregnancies. particularly when the specimens were contaminated with blood. Similarly, measurement of acetylcholinesterase (AChE) activity alone by three different methods also failed to eliminate the overlap between the two groups. In contrast, polyacrylamide gel electrophoresis revealed only a single band of ChE activity in 1408 out of 1410 fluids from pregnancies with a normal outcome whilst amniotic fluids from all 60 cases of open NTD. 6 out of 7 cases of exomphalos and 3 out of 4 cases of intra-uterine death gave the characteristic second faster-running AChE band. A qualitative gel method which requires the same amount of ChE activity to be loaded from each amniotic fluid is an effective method for pre-natal diagnosis of NTDs.     

用调查表与因果图法分析重整反应器DC301～304扇形管变形的原因

通过1991年、1992年、2001年3次大检修对重整反应器DC304扇形管下沉数据的实测,发现温度变化是扇形管变形的关健原因.     

BT20钛合金筒形件的UOE热成形

阐述了用UOE热成形BT20钛合金筒形件的特点。通过对BT20筒形件UOE热成形的实验研究,确定了BT20钛合金筒形件UOE热成形工艺过程,得到了一系列成形工艺参数及在成形过程中控制产品质量的措施。     

测试管法快速测定水中的磷酸盐

水中磷酸盐含量往往需要现场即时测定。通过研制一种测试管 ,从而能简便、快速的现场测定水中的磷酸盐。化学法测定时间需要 3～ 5h ,而该测试管法仅需 2～ 5min。分析成本大为降低     

圆管镦锻法兰成形的试验研究

通过对圆管镦锻法兰成形过程进行有限元数值模拟 ,分析了圆管坯料尺寸、摩擦等因素对圆管镦锻法兰成形过程中金属流动的影响及缺陷产生的原因。根据有限元数值模拟结果 ,进行了圆管镦锻法兰成形试验 ,数值模拟结果与试验结果具有较好的一致性。     

Alpha-fetoprotein and acetylcholinesterase in twins discordant for neural tube defect

Twins concordant for elevated alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) and discordant for neural tube defect (NTD) and sex are reported. A literature review reveals instances of termination of twin pregnancies with one normal and one abnormal fetus, partly based on concordant high AFP and positive AChE (although discordant on ultrasound examination). The levels of AFP and AChE in twin pregnancies are probably a function of the number of layers of fetal membranes separating twin sacs: dichorionic, diamniotic membranes allow transfer of AFP; monochorionic, diamniotic membranes allow transfer of both AFP and AChE. Cautious interpretation of biochemical findings and reliance on high resolution ultrasonography are suggested.     

The impact of screening for open neural tube defects in England and Wales

Using information derived from the voluntary system of notification of congenital malformations in England and Wales, the birth prevalence of anencephaly and spina bifida was estimated to have declined by 80 per cent from 31.5 to 6.2 per 10 000 between 1964–1972 and 1985. Over the same period, notified terminations of pregnancy with a suspected fetal central nervous system abnormality increased from less than 1 per cent to 56 per cent of neural tube defect births and central nervous system terminations combined, accounting for 31 per cent of the decline in births. Routinely collected national statistics provide a method for monitoring the impact of screening for open neural tube defects. However because they are incomplete and lack detail an alternative method of monitoring is needed. This paper includes an outline of such a method, together with the results of a pilot study designed to assess the feasibility of monitoring screening in the Oxford Region.     

High levels of maternal serum alpha-fetoprotein and human chorionic gonadotrophins leading to the diagnosis of combined neural tube defect and partial mole

A case of combined partial mole and neural tube defect is presented. The detection of high levels of both maternal serum (MS) alpha-fetoprotein (AFP) and human chorionic gonadotrophin (hCG) during the second trimester led to the ultrasonic demonstration of anencephaly, omphalocele, and partial mole. This is the first report of combined elevation of MSAFP and MShCG.     

含油污水的综合处理法及其应用

概述了竖向隔板分油法、蜂窝斜管分油法及磁性颗粒吸附过滤法 ,将这 3种方法结合处理某机修厂的含油污水 ,取得了满意效果。     

硫化氢气体快速检测方法研究

研究了快速监测硫化氢气体的新方法——硫化氢被动式检气管方法。该法是基于气体分子扩散(Fick)定律和化学吸收原理,将检气管内的海棉载体涂渍上对硫化氢有特效的显色剂(缓冲液G和醋酸铅)。测定时,硫化氢通过检气管端口扩散进入管内,在经过载体时,与载体上的显色剂发生反应,从而产生明显的颜色变化(浅黄色变成棕黑色)。检气管显色长度的平方与硫化氢质量浓度及采样时间的乘积在50~1500mg·m-3范围内成线性关系,从而快速监测环境中硫化氢的时间加权平均质量浓度。该检气管集采样与分析为一体,可快速测定硫化氢气体的质量浓度。与传统的采样分析方法比较,该检气管结构简单,操作方便,不受被测环境的空间大小、有无电源等影响;携带方便,利于外出测定和大面积布点测定。经过应用实验表明,该检气管具有较高的灵敏度,达到设计要求。