First-trimester amniotic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on normal amniotic fluids obtained at 4–15 weeks of pregnancy. Until 8 weeks, all the fluids were AChE-positive; the percentage of positive specimens decreased from 9 until 11 weeks and no positive specimen was found after 12 weeks. This method may allow early prenatal dignosis of neural tube defects after the 12th week.     

46,XX/46,XY chromosome complement in amniotic fluid cell culture followed by the birth of a normal female child

Experience indicates that the most likely explanation for a mixture of 46,XX/46,XY cells in an amniotic fluid sample is that of maternal cell contamination and that a normal male child is to be expected at birth. We report the birth of a normal female child following prenatal diagnosis of such a mixture. Extensive postnatal studies failed to reveal an XY cell line. The possible sources of the XY cell line are discussed, as are the various techniques that were applied in an effort to discover it's origin. Cross-contamination of samples could be ruled out and there was no evidence of an unsuspected twin pregnancy. It is clear from this case that not all 46,XX/46,XY results obtained in amniotic fluid can be assumed to represent maternal cell contamination and some effort should be made to eliminate other potential sources for such a mixture.     

First trimester amniocentesis between the seventh and 13th weeks: Evaluation of the earliest possible genetic diagnosis

Amniocentesis performed at the 12th week and later gives reliable results. The procedure can be performed using regimens developed for mid-trimester amniotic fluid (AF) cells. Extension to the 10th–11th week is, in principle, feasible. However, the high cytogenetic failure rate is a difficulty and despite a high clone count, the culture time is prolonged. The problem of the relatively high loss of AF could be overcome by cell filtration techniques and replacement of the fluid. Because of the short turnover rate of the AF, this may be unnecessary or replacement with an isotonic solution may be sufficient. (Pseudo)mosaicism appears to occur more frequently in early than in late amniocentesis. As yet, data are too sparse to allow a comparison with chorionic villus sampling. There are no reliable follow-up data from which to estimate the abortion rate and the number of embryonic malformations.     

Fetal nuchal fluid-physiological or pathological?—In pregnancies less than 17 menstrual weeks

For pregnancies less than 17 menstrual weeks, increasing amounts of nuchal fluid increase the risks of chromosome abnormalities with localized nuchal fluid, diffuse nuchal fluid, cystic hygroma, and fetal hydrops having chromosomal risks of 12, 23, 50, and 78 per cent, respectively. The ultrasound appearance of localized or diffuse nuchal fluid is not a specific discriminator, but a fluid depth of greater than or equal to 5 mm may be an indicator of increased risk of fetal chromosomal abnormalities. If the fluid depth is less than 5 mm, there is a stronger negative predictive value and negative likelihood risk of a fetal chromosome abnormality. Gestational age did not improve the fluid depth predictive value. Differentiation of physiological from pathological requires chromosome analysis, serial ultrasound evaluation, and good clinical examination as a newborn and possibly as a young child. Long-term follow-up of those cases identified with resolving nuchal fluid abnormalities is not available and is required for a complete understanding of physiological and pathological aetiologies. Genetic counselling for fetal nuchal fluid would be recommended.     

循环高速流态化反应器低温脱硫研究

介绍了用循环高速流态化反应器促进在潮湿气氛中氧化钙与SO2反应的研究成果。实验证明,在影响脱硫率的诸因素中,钙硫比、气体相对湿度和SO2浓度作用最大,反应温度次之,气速(075～125m/s范围内)影响最小。实验还表明:按指定的钙硫比(15～25),将氧化钙加入反应器后,脱硫率不断上升,在20min达到了45%～50%,远远超过相似条件下气流床脱硫率20%的水平;继续加料至第40min时,脱硫率已上升到75%,并有继续升高的潜力。介绍了用循环高速流态化反应器促进在潮湿气氛中氧化钙与SO2反应的研究成果。实验证明,在影响脱硫率的诸因素中,钙硫比、气体相对湿度和SO2浓度作用最大,反应温度次之,气速(075～125m/s范围内)影响最小。实验还表明:按指定的钙硫比(15～25),将氧化钙加入反应器后,脱硫率不断上升,在20min达到了45%～50%,远远超过相似条件下气流床脱硫率20%的水平;继续加料至第40min时,脱硫率已上升到75%,并有继续升高的潜力。     

大气有机污染物的吸附剂富集—超临界流体萃取—色质联用分析

本文研究了有机吸附剂ＧＤＸ－１０１１，ＧＤＸ－１０２，ＧＤＸ－５０２富集大气中痕量有机污染物的超临界流全萃取方法，比较了三种吸附剂富集大气中有机物的主要成分其超临界流体的萃取效率，并与索钉抽提法做了对比，结果表明，ＧＤＸ－５０２吸附有机物组分最多，超临界流体萃取对ＧＤＸ－５０２的解吸效率也最高，对被ＧＤＸ－５０２吸附的可以定量分析的３５种有机物的平均回收率为８４．５－１０８．９％，相对标准偏差为１     

A Computational Fluid Dynamics Approach for Urban Area Transport and Dispersion Modeling

A simulation tool has been developed to model the wind fields, turbulence fields, and the dispersion of Chemical, Biological, Radiological and Nuclear (CBRN) substances in urban areas on the building to city blocks scale. A Computational Fluid Dynamics (CFD) approach has been taken that naturally accounts for critical flow and dispersion processes in urban areas, such as channeling, lofting, vertical mixing and turbulence, by solving the steady-state, Reynolds-Averaged Navier–Stokes (RANS) equations. Rapid generation of high quality cityscape volume meshes is attained by a unique voxel-based model generator that directly interfaces with common Geographic Information Systems (GIS) file formats. The flow and turbulence fields are obtained by solving the steady-state RANS equations using a collocated, pressure-based approach formulated for unstructured and polyhedral mesh elements. Turbulence modeling is based upon the Renormalization Group variant of the k–ε model (k–ε RNG). Neutrally buoyant simulations are made by prescribing velocity boundary condition profiles found by a power–law relationship, while turbulence quantities boundary conditions are defined by a prescribed mixing length in conjunction with the assumption of turbulence equilibrium. Dispersion fields are computed by solving an unsteady transport equation of a dilute gas, formulated in a Eulerian framework, using the velocity and turbulence fields found from the steady-state RANS solution. In this paper the model is explained and detailed comparisons of predicted to experimentally obtained velocity, turbulence and dispersion fields are made to neutrally stable wind tunnel and hydraulic flume experiments.     

湘中锡矿山式锑矿成矿物质来源探讨

本文从地层含矿性、同岩浆活动的关系及同位素组成特征等几个方面进行分析 ,以阐明湘中锡矿山式锑矿成矿物质来源于构造岩浆活化作用形成的区域性深部上升流体。虽然赋矿层位相对集中 ,但不存在明显的锑矿源层。铅同位素研究表明矿石铅来源于深部均化条件下的铅同位素演化系统 ,与围岩地层铅同位素明显不同。硫同位素显示矿石硫为均一化程度较高的混合深源硫。包裹体水氢、氧同位素组成介于大气降水与初生水之间 ,为混合水类型     

Amniotic fluid alpha-fetoprotein and acetylcholinesterase measurements in pregnancies associated with gastroschisis

In this study we define for the first time the distribution of alpha-fetoprotein levels and acetylcholinesterase ratios in amniotic fluid samples associated with fetal gastroschisis. Elevated alpha-fetoprotein levels and positive acetylcholinesterase measurements are found in virtually all cases, indicating that these combined measurements are highly reliable in detecting this lesion.     

略谈遂昌—龙泉火山岩区金的成矿条件和成因

本文主要记述了治岭头、八宝山和庄山矿床(点)成矿的物化条件。它们的成矿温度主要集中于150—300℃,为中、低温矿床。成矿压力集中于120—30巴(12—30MPa),成矿深度约为0.3—0.9km。气体组分的还原参数较低,平均为0.4,fO_2约为10~(-38)—10~(-41),成矿溶液为弱酸性。流体包裹体、氢氧同位素,δD(％)为-58至-91,δ~(18)OH_2o(‰)为+3至-9。成矿溶液主要由大气降水(或地下水)和部分热液混合组成。