直接法测定大气中的非甲烷烃

介绍了在２个监测点，用直接法测定大气中的非甲烷烃。测定方法的检出限可达０．００６５ｍｇ／ｍ＾３，在线性范围０－１０ｍｇ／ｍ＾３时，线性相关系数为０．９９９５，相对标准焦虑差为２．８％。结果表明，由于大气逆温层、工业排放源、汽车排气对非甲烷烃的浓度变化产生影响，其日变化曲线呈双峰形。     

Characteristics of phosphorus chemistry and its geographical distribution in the Haihe River valley,North China

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Amniotic fluid alpha-fetoprotein levels and prenatal diagnosis of autosomal trisomies

Pregnancies with fetal trisomy 21 have been associated with low amniotic fluid alpha-fetoprotein levels (AFAFP). This observation led to the suggestion that low AFAFP levels be used as a criterion for completion of a chromosomal analysis in patients who are not otherwise at increased risk for a fetal chromosome abnormality and in whom karyotyping might not have been completed for economic reasons. In order to assess the usefulness of such criteria, we reviewed the AFAFP levels of 90 cases of fetal trisomy 21, 23 cases of trisomy 18, and 10 cases of trisomy 13. These were compared with 2400 control samples with normal chromosome constitution. AFAFP levels were generally lower in pregnancies with trisomy 21, showing a median value of 0·72 MoM. However, 40 per cent of the trisomy 21 samples had AFAFP values greater than 0·8 MoM and 20 per cent were over 1·0 MoM. These data imply that over 50 per cent of Down syndrome cases might have been missed using a cut-off level of 0·70 MoM for completion of chromosome analysis. Using a higher cut-off level will leave only a small percentage of samples unkaryotyped. The distribution of AFP levels in trisomy 13 and 18 is no different from controls; we therefore believe that fetal karyotyping should be completed in every amniotic fluid sample obtained.     

炼油装置运行周期评估技术及应用

炼油装置运行周期评估技术通过统计、分析装置故障数据,计算特定时间段装置的可靠性,进而获得装置可靠性随时间的变化规律和装置可靠性最差设备排序。介绍了该技术在某常减压装置的应用,应用结果表明,该评估技术为科学确定炼油装置运行周期提供了决策依据。     

Initial Homotypic Cell Pair Adhesion in Regenerating Hydra Facilitates Subsequent Adhesion of Homotypic Cells

 In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic cells to adhere. Received: 25 August 1999 / Accepted in revised form: 11 January 2000     

煤矸石制非烧结砖的可行性研究

从实验室试验和工业性试验出发， 煤矸石制非烧结砖的可行性。研究结果表明，用煤矸石和适量固化剂制成的非绕结砖经过２８ｄ自然养护后，其质量和放射性均符合国家有关标准。利用煤矸石非烧砖无 技术上还是经济上都是可行和有利的。     

Prenatal diagnosis in two cases of de novo complex balanced chromosomal rearrangements. Three-year follow-up in one case

We report two cases of apparently balanced complex de novo chromosomal rearrangements (BCCR) detected prenatally at 17 weeks and 10 weeks of gestation, respectively. Chromosomes were studied using GTG-banding and fluorescent in situ hybridization (FISH). In one case four chromosomes and in the other case three chromosomes were involved in the rearrangements. One of the pregnancies was terminated and no external or internal abnormalities were detected at autopsy. The other pregnancy continued to term. Level III ultrasound examination showed no abnormalities. The child is now 3 years old and has neither congenital anomalies nor evidence of delayed psychomotor development.     

Prenatal diagnosis of β thalassaemia by reverse phase HPLC

Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography.