铝合金管缩为长锥管金属沿轴向延伸和壁厚变化规律的研究

对铝合金管在无芯棒情况下,缩为内锥为2.5°左右长锥管的金属沿轴向延伸率和壁厚变化规律进行研究,提出了相应的计算公式,可做为确定管坯长度和模具型腔尺寸的依据.     

The early diagnosis of neural tube defects

The sonographic diagnosis of fetal neural tube defects (NTDs) has been enhanced by the recognition of associated brain and skull anomalies. Previous reports have found these anomalies to be accurate in predicting spina bifida after 16 weeks' gestation, and an inverse correlation was suggested between the presence of these sonographic markers and gestational age. Therefore, we assumed that early second-trimester sonography would be at least as accurate as that performed after 16 weeks' gestation. To examine this hypothesis, we looked for the presence of these cranial sonographic markers suggestive of open NTDs in 8011 low-risk cases, using transvaginal sonography (TVS), between the 12th and 17th week of gestation (menstrual age). Fetal NTDs were identified in ten cases (l.25%o). The NTDs were cervico-cranial in three, lumbo-sacral in six, and thoracal in one of the ten cases. None of the seven cases examined was dyskaryotic. Cerebellar dysmorphism, ‘banana’ sign, cerebellar absence, and hypoplasia were detected in all the low NTDs, usually before the detection of the spinal lesion. All the sonographically diagnosed malformations were confirmed by post-abortal examination except in one case, where the patient decided to continue the pregnancy and refused follow-up. We therefore conclude that transvaginal sonographic examination of the fetal skull before the 17th week of gestation is an accurate method for the detection of low NTDs.     

Alphafetoprotein,cholinesterases and rapidly adhering cells in the prenatal diagnosis of neural tube defects

Amniotic fluid cholinesterases tested on polyacrylamide gel and rapidly adhering cell analysis were compared in their efficiency at diagnosing fetal neural tube defects in three cases where the alphafetoprotein results were equivocal. While rapidly adhering cells were also equivocal, the cholinesterases consistently gave a clear indication of fetal abnormality.     

Prenatal sonographic diagnosis of diastematomyelia in a diabetic woman

Diastematomyelia is a structural anomaly which concerns primarily the spine and secondarily the nervous structures contained in it. A case of early prenatal diagnosis (20th week) by ultrasound of diastematomyelia with associated diplomyelia in a diabetic woman is reported. Radiological and pathological examination of the fetus after therapeutic abortion confirmed the diagnosis.     

Adverse perinatal outcome in patients screen-positive for neural tube defects and fetal down syndrome

An association between various abnormal mid-trimester maternal serum analyte values and adverse perinatal outcome has been reported. From an original sample of 14 857 women, we observed five women who were ‘screen-positive’ for both neural tube defects [maternal serum alpha-fetoprotein (MSAFP) ≥2·5 multiples of the median] and Down syndrome [risk ≥1/274 using MSAFP, maternal serum unconjugated oestriol (MSuE3), maternal serum human chorionic gonadotropin (MShCG), and maternal age]. The four patients who elected to undergo amniocentesis all demonstrated both normal karyotype and normal amniotic fluid AFP levels. All five cases were associated with intrauterine growth retardation (IUGR) and abnormal pregnancy outcomes. Two cases exhibiting severe IUGR on ultrasound examination were terminated at 19·1 and 21·2 weeks, respectively; the former also exhibited fetal calcifications and positive maternal serology for toxoplasmosis. In another case, fetal demise occurred at 36 weeks' gestation in a patient who had been treated for syphilis in the second trimester. Neither infection was confirmed in fetal tissue studies. Though resulting in live births, the remaining two cases required operative deliveries; emergency Caesarean sections for fetal distress were performed at 38 and 32 weeks, respectively, the latter case being associated with severe pre-eclampsia. We conclude that elevated mid-trimester MSAFP levels concurrent with maternal serum analyte values associated with increased risk for fetal Down syndrome may presage a poor perinatal outcome, particularly IUGR and possibly congenital infection.     

加热炉盘管的腐蚀与防护

加热炉通常采用原油或渣油为燃料,对炉管内流过的原油进行加热,以降低原油黏度,减少输送阻力.炉内盘管在高温及腐蚀性介质的作用下,常会发生腐蚀穿孔.对腐蚀发生的位置、原因进行了分析,并有针对性地提出了防护改进措施.     

基于LabVIEW和Arduino的无人机辐射监测系统设计与实现

目的克服传统环境核辐射监测的局限性,设计一种搭载GM计数管的固定翼无人机进行高空远距离环境核辐射剂量率监测的系统。方法系统通过编程简单、拓展强等开发特点的Arduino单片机完成探测器的硬件设计,同时利用LabVIEW的强大VISA通讯模块实现地面站的设计,最后借助无人机自驾仪Pixhack以实现对无人机稳定可靠控制。结果系统地面站操作界面简洁,测量数据图表直观。探测器对于放射源具有较好的计数响应。Pixhack对飞行平台有良好的稳定和控制作用。结论系统借助GM计数管作为辐射探测器探头,能够完成高空远程辐射监测任务,在结构设计仍具有很大的拓展空间,可满足日常环境核辐射本底剂量率普查,以及核应急、大范围辐射监测、远程辐射监测等任务。     

Amniocentesis carried out for neural tube indications in South Wales 1973–1981: Outcome of pregnancies and findings in the malformed abortuses

The 2872 second trimester amniocenteses followed by amniotic alphafetoprotein (AFP) estimations carried out in South Wales between 1973 and 1981 on women known to be at increased risk for neural tube defect (NTD) and those who had a raised serum AFP level in an NTD screening programme led to the identification of 78 pregnancies of a fetus with anen-cephalus, 61 with ‘open’ spina bifida, 8 with gastroschisis, 3 with exomphalos, 2 with encephalo-cele and 6 with chromosome abnormality. Pregnancies of fetuses having 4 potentially identifiable NTDs were missed because of an equivocal AFP level and there were two false positive results leading to the termination of one normal fetus. It is emphasized that both the latter problems of one normal fetus. It is emphasized that both the latter problems would not have occurred had gel-electrophoresis for isoenzymes of acetyl cholinesterase been available. Follow-up of pregnancies showed that 7 children with ‘closed’ NTD and 3 with congenital hydrocephalus were born. The anencephalics and the ‘open’ spina bifidas had a more florid lesion than is usual at term. Nearly all the spina bifidas were associated with hydrocephalus, often severe and with an obvious Arnold-Chiari malformation. All but 13 had leg or back deformation or malformations in other systems, mostly in the renal tract.