XII.—The upper Valentian trilobite fauna of Shropshire

Summary

Records of ten species of Sosylus collected in Nigeria are given, with details of distribution, host trees and platypodid associates. The Sosylus fauna of Nigeria appears to lie between that of Ghana and the Congo in species composition. Comment is made on the close association that some Sosylus species have with their platypodid hosts.     

Fission Yield Data Systematics for ^238U

Based on the mass distribution data up to 200 MeV measured by Zoner with kinetic energy method （corrected）, the systematics on dependence of chain yield on incident neutron energy for each mass number A with a linear and quadric function was studied. And also the systematics of mass distribution on mass A and incident neutron energy was investigated by using 5 （or 3 ） Gaussian model. A code of nonlinear squared least method was developed and the parameters were deduced by fitting the experimental data. The calculated results with the parameters obtained could reproduce the experimental data used well. But comparisons with the data measured by radiochemistry method show some systematical difference. It is shown that there is some systematical difference between the measured data with kinetic and radioactive nuclide methods, the masons of which need to be investigate further.     

拉萨河铀同位素分布特征与环境指示意义

水体环境中铀及其同位素含量的变动对于区域生态环境的保护具有重要意义。目前,对于处于环境敏感区的拉萨河水体中铀及其同位素的研究鲜有报道。为了解拉萨河流域水体中铀及其同位素的分布特征,利用拉萨河中下游和堆龙曲支流2017年7月采集的16个采样点的水样,采用电感耦合等离子体质谱仪（ICP-MS）Element 2测量得到水样中的铀及同位素(238U、235U和234U)含量并进行分析。结果表明,拉萨河水体中铀浓度显著高于世界河流铀浓度均值,与青藏高原河水中铀浓度相当,略低于黄河干流河水中铀浓度。铀及其同位素与K+有同源性,与Mg2+及SO42-有异源性,而与其它水化学参数无显著相关关系。拉萨河水体中235U和238U具有很好的相关性,未发生显著的同位素分馏现象。拉萨河水体出现较高的(234U/238U)AR值,最主要原因是水体中234U的富集或者流失,在水-岩交换作用的影响下234U在α反冲作用下易于进入水体。羊八井附近采样点具有高铀浓度的特点,反映出其水体环境具有较好的氧化条件。     

W.K.B近似和δ势垒近似下_∧~(238)U超核裂变中∧超子能级的计算

本文用高斯势垒和W.K.B近似方法,以及&势垒近似方法分别计算超核裂变过程中的∧超子的能级。     

用1—苯基—3—甲基—4—苯甲酰基—5—吡唑啉酮从硝酸中萃取痕量钍

用1－苯基－3－甲基－4－苯甲酰基－5－吡唑啉酮（PMBP）为萃取剂,^234Th作示踪剂,完成了在硝酸介质中痕量钍溶剂萃取行为的研究。在^234Th萃取效率与酸度、萃取剂浓度、平衡时间等依赖关系的条件实验的基础上,获得了萃取钍的最佳条件。使用改进的PMBP萃取钍的流程,从^18O离子辐照过的铀靶中分离钍,钍样品的γ射线单谱显示绝大部分反应产物和大量铀的去除是满意的。     

Export of particulate organic carbon estimated from234Th-238U disequilibria and its temporal variation in the South China Sea

Activities of²³⁴Th and nutrient concentrations in the upper 500 m water column were measured at a time-series station in the South China Sea over a time span of 12.3 d. Results showed a reduction of dissolved²³⁴Th and an overall increase of particulate²³⁴Th during the period. Meanwhile, activities of total²³⁴Th kept fairly constant, implying rapid transformation of²³⁴Th between the dissolved and particulate forms. Vertical profiles of total²³⁴Th showed evident deficit of²³⁴Th relative to²³⁸U in the upper 500 m water column. Using an irreversible steady-state model of thorium scavenging, export fluxes of particulate organic carbon (POC) corresponding to time pointsT ₁ andT ₂ were estimated to be 46.5 and 13.1 mmolC · m⁻² · d⁻¹. It was demonstrated that the estimation of POC export was greatly dependent on the POC/²³⁴Th_P ratios and the bias caused by the different models of²³⁴Th scavenging, however, was considered to be of minor importance.     

Variability of β-amylase isoenzymes within a collection of inbred lines of rye (Secale cereale L.)

Summary Within one collection of 18 inbred rye lines, seven distinct isoenzymatic patterns of 238/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-amylase were found, and five of them formed a group of similar patterns shifting to distinct positions in the gel. It was proved that the shift of the pattern was due to genetic factors. In crossed immunoelectrophoresis, drastic differences were shown in the quantity of the different 238/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-amylase constituents. No antigenic differences could be demonstrated between the analyzed isoenzymes.