烟气连续排放监测系统（CEMS）比对监测工作探讨

以陕西省18家30万kW以上火电机组自动监测仪器设备、比对监测的结果作为参考依据,指出CEMS比对监测存在缺乏统一管理、监管薄弱、监测方法不同、设备安装位置不规范、参数缺项的问题,并针对问题提出规范设备供应商、严把CEMS验收关、加强监管、贯彻执行国家相关文件及技术规范、强化环境执法等具体建议。     

海洋水质在线监测系统中硝酸盐测量方法比较

硝酸盐是海洋水质监测的重要指标,目前在海洋水质在线监测系统中搭载的硝酸盐在线分析仪的种类较多,采用的测量原理也不尽相同.选取了 3种采用不同测量方法的代表性硝酸盐分析仪[氯化钒还原比色法硝酸盐分析仪、二乙烯三胺五乙酸还原比色法(DTPA)硝酸盐分析仪、紫外分光光度法硝酸盐分析仪],结合各自的测量原理、化学试剂特性等,就...     

An experimental study of an LPG tank at low filling level heated by a remote wall fire

This paper describes an experimental study of 2300 L pressure vessels exposed to remote fire heating by a natural gas fuelled wall fire simulator. The tanks were filled to 15% capacity with commercial liquid propane. The flame intensity and distance were varied to study the effect of different heating levels on the tank and its lading.The fire simulator is first characterized with tests including fire thermocouples, radiative flux meters and thermal imaging. With the appropriate positioning of a target tank it is possible to get very realistic fire heat fluxes at the tank surface.Three tests were conducted with the 2300 L tanks filled to 15% capacity with propane. The tanks were positioned at three different distances from the wall fire resulting in measured average peak heat flux at the tank surfaces ranging between 24 and 43 kW m^?2. The data shows rapid rise in vapour space wall temperatures, significant temperature stratification in the vapour space, and moderate rate of pressure rise. These results provide excellent data for the validation of computer models used to predict the response of pressure vessels exposed to moderate heating from a remote fire.     

The Relevance of Error Analysis in Graphical Symbols Evaluation

In an increasing number of modern tools and devices, small graphical symbols appear simultaneously in sets as parts of the human-machine interfaces. The presence of each symbol can influence the other’s recognisability and correct association to its intended referents. Thus, aside from correct associations, it is equally important to perform certain error analysis of the wrong answers, misses, confusions, and even lack of answers. This research aimed to show how such error analyses could be valuable in evaluating graphical symbols especially across potentially different user groups. The study tested 3 sets of icons representing 7 videophone functions. The methods involved parameters such as hits, confusions, missing values, and misses. The association tests showed similar hit rates of most symbols across the majority of the participant groups. However, exploring the error patterns helped detect differences in the graphical symbols’ performances between participant groups, which otherwise seemed to have similar levels of recognition. These are very valuable not only in determining the symbols to be retained, replaced, or re-designed, but also in formulating instructions and other aids in learning to use new products faster and more satisfactorily.     

Biamnial elevated alpha-fetoprotein and positive acetylcholinesterase in twins,one with anencephaly

Anencephaly in twin B was accompanied by elevated amniotic fluid alpha-fetoprotein (AFP) and a positive acetylcholinesterase (AChE) band on gel electrophoresis in both twin sacs, although twin A was normal. AChE results did not help distinguish the false positive AFP in this set of twins, implying that AChE may diffuse transamniotically as has been previously postulated for AFP. In light of the low concordance rate for neural tube defects in twins, patient counselling in this situation must include the information that AFP and AChE may be falsely elevated in normal twin when the other twin has a neural tube defect.     

Prenatal detection of multiple copies of a familial supernumerary marker chromosome

Direct preparations and long-term cultures from a chorion villus biopsy, taken because of a known maternal additional marker chromosome, showed a 48,XX,+mar,+mar karyotype in all cells examined. The same karyotype was revealed in a subsequent amniotic fluid sample and in cord blood at delivery. Detailed examination of the child at delivery and at 1 year of age showed no evidence of phenotypic abnormality or developmental problems.     

An assessment methodology for successional systems. II. Statistical tests and specific examples

This paper presents a dynamic framework for environmental assessment when the system under study is undergoing successional change. Successional differences between sites for which one wishes to detect a difference because of a treatment are essentially confounding factors. We show how successional changes over the study period or resulting from differences in study site plot ages can be factored out by developing a null model of expected behavior over time. The null model for change in state with time is characterized in terms of a stochastic envelope around a nominal trajectory. Specific tests for the detection of trends associated with succession are described and illustrated on example data. It is concluded that the methods developed work particularly well for laboratory microcosm data.     

Comparison of fetal and maternal chromosome polymorphisms: Applications in prenatal diagnosis

By comparing the polymorphisms of Q-banded karyotypes of a mother and her female fetus, it is possible to confirm that maternal cell contamination is a rare event in prenatal diagnosis. The frequency with which any given polymorphism is distinctive is directly correlated to its prevalence in the population. Hence, since the polymorphisms on bands 3c, 13p and 21s are the most prevalent in the population, comparison of these maternal bands with the corresponding fetal ones is most likely to yield a distinctive pattern between a mother and her female fetus. However, in light of the rarity of maternal cell contamination, comparison of chromosomal polymorphisms is not cost-effective for all cases, and is recommended only for high-risk situations such as prenatal diagnosis of recessive or X-linked diseases, where maternal age is over 40, or when amniotic fluid is grossly bloody.     

Separation of amniotic fluid cell types in primary culture by percoll density gradient centrifugation

Amniotic fluid cells obtained by transabdominal amniocentesis at 15–17 weeks of gestation and cultured for 15 and 21 days were separated into three fractions by density gradient centrifugation in Percoll. Each fraction (or peak) corresponded to the following densities: peak A, 1·02–1·03 g/ml; peak B, 1·04–1·05; peak C, 1·05–1·06. Peak A was composed of both non-viable and viable cells; the latter adopted the morphology of epithelial cells in culture. Peak B contained a mixture of fibroblasts and epithelioid cells and peak C had only epithelioid cells. The variability of N-acetyl-β-hexosaminidase and alkaline phosphatase activities was reduced in peaks B and C as compared to that of peak A and of unseparated cells suggesting that more defined and homogeneous cell types for enzymatic determinations can be obtained by centrifugation in Percoll density gradient. In prenatal diagnosis of biochemical defects, the separation of cells would permit a more precise diagnosis by eliminating enzyme variability due to the presence of different cell types or non-viable cells.     

Can fetal gastroschisis always be diagnosed prenatally?

Fetal gastroschisis is regarded as a relatively straightforward ultrasound diagnosis. We report two cases of infants born with undiagnosed gastroschisis despite several detailed prenatal assessments following raised serum alphafetoprotein measurements. In both cases, the bowel was healthy with no evidence of long-term herniation through the abdominal wall and primary surgical correction was successful. Gastroschisis has previously been classified as ‘antenatal’ and ‘perinatal’, and we conclude that the latter type is not always possible to diagnose prenatally.