Elemental composition of sediment cores from a mangrove environment using neutron activation analysis

The geochemistry of Sepetiba Bay was studied in four sediment cores using a multi-element approach. Two cores were sampled in the more contaminated eastern part of the bay and two cores were sampled in the western region. The aim was to determine whether less common elements like the rare earths or the actinides are associated with contaminant metals like zinc in the Bay. Samples were analysed by instrumental neutron activation analysis that permits the quantification of total concentrations of metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), rare earth elements (Ce, Eu, La, Lu, Sm and Yb), actinides (Th, U), non-metals and semi-metals (As, Br). Organic carbon and total sulphur were also analysed. The results show very strong zinc contamination in the top layers (more than 1000 μg g⁻¹) and background concentrations in the bottom (15 μg g⁻¹). Elements like chromium which would be expected to be released by the heavy industries of Sepetiba Bay, did not show a contamination profile, and concentrations remained close to those of natural environments. No evidence of any association between the zinc and other potential contaminant elements could be identified in this work.     

核技术在中成药微量元素学中的应用

利用钴— 6 0放出的伽玛射线对中成药进行灭菌保鲜这一核技术 ,目前已被广泛应用。在灭菌过程中 ,对于不同的照射剂量、不同的辐照时间及辐射前后中成药中的微量元素是否会产生某些变化 ?有没有带来新的毒副作用 ,这是人们普遍关心的问题。本文就利用中子活化分析的方法对以上问题进行了探讨     

中华绒螯蟹眼柄神经内分泌细胞胞吐分泌活动的实时监测

首次应用膜片钳技术 ,通过监测细胞膜电容变化的方法实时测定去极化电刺激诱导的单个中华绒螯蟹眼柄神经内分泌细胞释放甲壳动物高糖激素 (CHH)的胞吐分泌活动。结果表明 ,膜电容检测法适用于中华绒螯蟹眼柄神经内分泌细胞胞吐分泌活动的监测 ,在细胞的分泌过程中清晰地记录到膜电容的增加。膜电容的增加与去极化时间相关。去极化2 0ms,细胞的膜电容开始增加 ;2 2 0ms的去极化诱导细胞分泌CHH达到饱和 ,膜电容增加约(5 2 1± 3 6 )fF(n =5 )。不同幅值去极化电压诱导细胞分泌活动监测结果表明 ,只有当去极化电压超过钙离子通道激活阈值才会引起细胞膜电容的增加。这一结果提示中华绒螯蟹眼柄神经肽类激素为细胞外钙离子依赖性分泌。     

青岛崂山碱性花岗岩的元素地球化学研究

本文报道了青岛崂山碱性花岗岩的稀土元素和微量元素地球化学特征。利用仪器中子活化分析了崂山碱性花岗岩的稀土元素和微量元素含量,并依此讨论了崂山碱性花岗岩的成因和物质来源。     

浮式海洋平台运动实时预报

本文应用周期序列分析理论建立模型，提出了一种对海洋平台在随机海面上运动预报的新方法：周期图法，计算结果表明预报步长可达１０秒以上，增加了预报时间，足以供飞机驾驶员进行决策。     

大洋多金属结核和深海沉积物标准物质中铂族元素的中子活化分析

采用镍锍试金预富集中子活化分析方法,测定了大洋多金属结核标准物质ＧＳＰＮ２、ＧＳＰＮ３和深海沉积物标准物质ＧＳＭＳ２、ＧＳＭＳ３中的铂族元素;根据大洋样品成分特征,对常规的镍锍试金配方和熔炼条件作了改善;计算了活化分析中的铂族元素干扰核反应,校正了Ａｕ对Ｐｔ的二级干扰;选用羰基化镍粉配料,降低了铂族元素空白值。用国家一级标准物质ＧＢＷ０７１０２作了对照分析,结果与标准值相符。     

New timing parameters and positions for 16 southern radio pulsars

We report timing observations on 16 pulsars obtained using the Ooty Radio Telescope operating at 327 MHz. Using these observations, spanning over a year, we have obtained values of period derivatives for the first time and refined the estimates of the periods for all pulsars in this sample. We also report improved positions for all cases where the earlier position estimates had an uncertainty of a few arcmin.     

Towards gravitational wave asteroseismology

We present new results for pulsating neutron stars. We have calculated the eigenfrequencies of the modes that one would expect to be the most important gravitational wave sources: the fundamental fluid f mode, the first pressure p mode and the first gravitational wave w mode, for twelve realistic equations of state. From these numerical data we have inferred a set of 'empirical relations' between the mode frequencies and the parameters of the star (the radius R and the mass M ). Some of these relations prove to be surprisingly robust, and we show how they can be used to extract the details of the star from observed modes. The results indicate that, should the various pulsation modes be detected by the new generation of gravitational wave detectors that come online in a few years, the mass and the radius of neutron stars can be deduced with errors no larger than a few per cent.     

Local pulsars: A note on the birth-velocity distribution

We explore a simple model for the representation of the observed distributions of the motions, and the characteristic ages of the local population of pulsars. The principal difference from earlier models is the introduction of a unique value,S, for the kick velocity with which pulsars are born. We consider separately the proper motion components in galactic longitude and latitude, and find that the distributions of the velocity components parallel and perpendicular to the galactic plane are represented satisfactorily byS = 200 km/sec, and leave no room for a significant fraction of much higher velocities. The successful proposition of a unique value for the kick velocity may provide an interesting tool in attempts to understand the physical process leading to the expulsion of the neutron star. This paper is an extended analysis of the talk presented by A. Blaauw at the Raman Research Institute on 20th February, 1996.     

Comparison of the large-scale clustering in the APM and the EDSGC galaxy surveys

We present the results of a numerical study of the fluid f, p and the gravitational w modes for increasingly relativistic non-rotating polytropes. The results for f and w modes are in good agreement with previous data for uniform density stars, which supports an understanding of the nature of the gravitational wave modes based on the uniform density data. We show that the p modes can become extremely long-lived for some relativistic stars. This effect is attributed to the change in the perturbed density distribution as the star becomes more compact.