摘要:本文介绍我们研制的放射性长距离地下管道检漏仪的工作原理及电路结构、仪器特点、检漏方法和几个主要参数的确定.仪器的检漏灵敏度可达185kBq(5µCi),定位准确度每km在2.5m之内,适用于口径为15或20 cm (6英寸或8英寸)的地下轻油(汽油、煤油和柴油)管道及工业用水管道的检漏。一次检测管道长度可达50km.
摘要:In order to study the mechanism of the imbalance of amino acid metabolism during hepatic failure, a stable isotope tracer method for observing simultaneously the metabolic kinetics of several amino acids has been established. 15N-L-Ala, (2,3-D3)-Leu and (2, 3-D3)-Phe were chosen as nonessential, branched chain and aromatic amino acids. A single iv injection of 40 mg 15N-Ala, 20 mg deuterated Leu and 20 mg deuterated Phe was given to each human subject. Blood samples were taken just before and at different times (up to 60 min) after the injection. Total free amino acids were isolated from the plasma with a small dowex 50×8 column and converted to trifluoroacetyl derivatives. Their abundances were then analyzed with a GC-MS system and typical double exponential time course curves were found for all the three labelled amino acids. A two-pool model was designed and applied for compartmental analysis.Significant changes were found in the kinetic parameters of Phe and Leu in patients with fulminant hepatitis or heptic cirrhosis. The half-lives of both Phe pools were longer and the pool sizes were larger than normal subjects, while the half-lives and pool sizes of Leu changed in the opposite direction. No marked change was found in Ala. The significance of intracellular imbalance of Phe and Leu metabolism was discussed. It is evident that the combination of GC-MS technique and multiple-tracers labelled with stable isotopes is of great potential for similar purposes.