煤层注水降低综采工作面煤尘浓度的研究

在深入研究官地矿９＃ 煤渗透特性的基础上,提出动压预注水的煤层注水方案与参数,并在官地矿进行了工业性试验,取得了降低综采工作面煤尘浓度６０％ 以上的明显效果。它对我国煤矿有效实施煤层注水、降低工作面粉尘浓度具有实际指导意义     

Complications of cordocentesis in high-risk pregnancies: Effects on fetal loss or preterm delivery

Between 1990 and 1993, 166 cases underwent cordocentesis and were followed for at least the following 4 weeks in the Prenatal Diagnosis and Therapy Centre of Vienna University. The indications for the procedure were structural malformations in 46·4 per cent of the cases, other high-risk diagnoses in 48·8 per cent, and maternal age over 35 years in only 4·8 per cent. We investigated retrospectively all cases of complications resulting in fetal loss or preterm labour. Abortion, intrauterine fetal death, chorioamnionitis, and preterm delivery occurred in 0·6, 5·4, 0·6 and 9·0 per cent of these cases, respectively, adding up to a total of 26 cases (15·7 per cent). Although this rate looks relatively high, 20 of the 26 cases had already displayed signs implying a complicated prognosis. Neither maternal age, gestational age, number of attempts, nor placental location correlated with fetal loss or preterm delivery. Significantly higher rates of fetal loss or preterm delivery were observed when cordocentesis was performed in cases diagnosed as duodenal/intestinal stenosis or hydrops–ascites–hydrothroax/hygroma colli (P=0·0488 and P=0·0005). The frequency of complications did not decrease as the experience of the operators increased.     

Elevated alpha-fetoprotein and human chorionic gonadotropin as a marker for placental trisomy 16 in the second trimester?

In a series of 2961 consecutive cases with second-trimester biochemical triple screening for Down's syndrome and neural tube defect (NTD), ten (0.3 per cent) showed an apparent increased risk for both conditions. Three cases had chromosomal abnormalities, namely trisomy 16 confined to the placenta. Since placental trisomy 16 as well as cases with increased alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) are associated with (intrauterine growth retardation (IUGR), oligohydramnios, and fetal demise, at least some cases with this atypical biochemical profile could be explained by this chromosomal abnormality. From our results we recommend that in cases with increased risk for both Down's syndrome and NTD, fetal karyotyping should preferably be done on a placental biopsy, especially when ultrasound in the absence of anomalies demonstrates early IUGR.     

Prenatal detection of X-linked ichthyosis by maternal serum screening for down syndrome

Maternal serum unconjugated oestriol (uE3) was measured in 15 375 pregnancies during 2 years of second-trimester risk assessment for Down syndrome using biochemical markers. Very low levels of uE3 (<0·1 MOM) were detected in 22 serum samples (0·14 per cent). Very low uE3 was associated with an adverse outcome in 13 pregnancies including fetal death and miscarriage (N=11), anencephaly (N=1), and Meckel—Gruber syndrome (N=1). Dry scales on the skin appeared in the first year of life in four boys. From dermatological diagnosis, prenatal uE3 levels, and pedigree analysis, it is concluded that at least 5 in approximately 7500 male births in the study population are affected by steroid sulphatase deficiency, which is the biochemical defect in X-linked ichthyosis. Very low uE3 levels in the second trimester are indicative of this disease in pregnancies with normal ultrasound findings.     

Early amniocentesis—a cytogenetic evaluation of over 1500 cases

We report our cytogenetic experience of 1554 early amniocenteses between weeks 11 and 14 of gestation, of which 44 per cent were performed prior to week 14. The mean culture time was 14·5 days. Karyotyping was successful in 99·7 per cent of cases. In 9·9 per cent of cases, there was pseudomosaicism with a high rate of loss of an X-chromosome and structural aberration of chromosome 1, which may be due to the Chang medium. The mosaic rate was 0·5 per cent. The overall aberration rate was 2·8 per cent. Our data confirm the reliability of early amniocentesis, which is a serious alternative to standard amniocentesis and chorionic villus sampling (CVS).     

Clinical and pathological factors in spontaneous abortion following chorionic villus sampling

Twenty-nine cases of spontaneous abortion following first-trimester chorionic villus sampling (CVS) were reviewed out of a series of 722 patients. Of the 29 cases, there were only four abnormal CVS results. Pathological examination was performed in 79 per cent of cases, and this did not identify any characteristic pathological feature associated with spontaneous abortion after CVS. There was no obvious difference in the pathological features following the transabdominal (TA) or the transcervical (TC) methods. The majority of miscarriages occurred within 4 weeks of the procedure, but 38 per cent of cases aborted between 7 and 14 weeks after CVS. The TC method was used in 22 patients; the TA in 6; and both methods in 1 patient. The TA method was associated with a significantly lower fetal loss rate than the TC method (TA 2 per cent, TC 9 per cent, p < 0.001).     

Prenatal karyotyping in malformed fetuses

Experience with prenatal karyotyping of 237 fetuses with sonographic evidence of malformation is reported. Abnormal karyotype was found in 40 cases (16-8 per cent): chromosomal aberrations were found in 19 of the 178 fetuses with an isolated structural anomaly (10-6 per cent) and in 21 of the 59 fetuses with multiple malformations (35-6 per cent). Detailed cytogenetic and morphological information concerning fetuses affected by omphalocele, duodenal atresia, hydrocephalus, multicystic kidney, unilateral hydronephrosis and cystic hygroma is reported. The need for a very careful ultrasound evaluation of fetal anatomy in these pregnancies is stressed, as the risk of a chromosomal anomaly depends mainly on the existence of more than one ultrasonically diagnosed structural defect.     

Convergent-flow tracer tests in heterogeneous media: combined experimental-numerical analysis for determination of equivalent transport parameters

In modeling transport within naturally heterogeneous aquifers, it is usually assumed that the transport equations valid at local scales can also be applied at larger scales. At larger scales, the heterogeneous domain is represented by an equivalent homogeneous medium. Convergent-flow tracer tests constitute one of the most frequently used field tests to estimate effective input parameters of equivalent homogeneous aquifers. Traditionally, statistical approaches applied to groundwater flow and solute transport have provided tools to estimate these equivalent parameters. These approaches are based on a number of simplifications including the assumption that the point transmissivity values follow a multilog-normal random function. Several investigators have found that this assumption may not be valid in many field cases. In order to study the applicability of the equivalent homogeneous formulation in a nontraditional stochastic field, a number of experimental and numerical studies were conducted. The results are used to determine the apparent values of porosity and dispersivity that would be obtained if convergent-flow tracer tests were conducted in a deterministically generated heterogeneous transmissivity field displaying anisotropy in the correlation structure. It is shown that in this particular heterogeneous media, apparent porosity strongly depends on connectivity rather than on transmissivity. This dependence on connectivity questions the theoretical results obtained in continuum equivalent fields to estimate effective porosity.     

Distribution of endocrine disruptors in the Llobregat River basin (Catalonia, NE Spain)

The Llobregat basin is a Mediterranean fluvial system with major agricultural, urban and industrial impacts. We combined chemical quantification by liquid chromatography–mass spectrometry with electrospray interface (LC-ESI-MS) and the recombinant yeast assay (RYA) assays to estimate the loads of endocrine disrupting compounds (EDCs) along the basin. Chemical analysis revealed maximum concentrations (at μg l⁻¹ level) of alkylphenols at the lower course of the Llobregat River, which correlated with high levels of estrogenic activity detected by RYA. Analysis by RYA and LC-ESI-MS of influent and effluent waters from four sewage treatment plants (STP) discharging into the basin showed the removal of 80–95% of EDCs by STP treatment. Chemical analysis data and RYA data showed a quasi-linear correlation, demonstrating the complementariness of both methods. Our data suggest that the concentrations of the analysed compounds were enough to explain the total estrogenicity of water and STP samples from the Llobregat basin.