人骨骼中~(228)Th、~(230)Th和~(232)Th含量的同时测定

本文介绍了用α谱仪同时测定人骨骼中~(228)Th、~(230)Th和~(232)Th含量的方法。样品用浓 HNO_3和 H_2O_3湿灰化,草酸钙共沉淀载带、CL-5208萃淋树脂和743阳离子交换树脂联合分离后,电沉积制源,在低温半导体α谱仪上测量。该方法对~(234)Th的全程回收率为95.0±1.7%,对铀和镭的去污系数分别为6.3×10~4和1.5×10~3,对~(228)Th、~(230)Th、~(232)Th 的探测下限分别为0.432、0.135和0.108Bq/kg(鲜重)。     

同位素中子源活化瞬发分析装置

一、基本原理自六十年代中期以来,中子活化瞬发γ射线元素分析技术(PNAA)得到人们广泛重视。与通常的中子活化分析(NAA)技术相比,它分析的是样品中的主要成分,若用同位素中子源,还可进行实时在线连续测定及现场分析。PNAA技术是用热中子与待测元素发生中子俘获反应,处于激发态的产物核在瞬间     

同位素稀释质谱法测定高放废液中的铀

用双同位素稀释质谱法测定高放废液中的微量铀,采用TBP/Kel-F粉反相分配色层法分离铀,双稀释剂分别为浓缩~(235)U及~(238)U,铀同位素丰度比的质谱测定相对标准误差优于0.1%,化学处理及质谱测定全流程铀的空白值为3×10~(-9)g,方法检测限对于铀为1×10~(-9)g,高放废液中微量铀测定结果不确定度为±2%。     

溶剂萃取分离锂同位素研究Ⅱ.苏丹Ⅰ-中性配位体协萃体系萃取分离锂同位素效应探讨

文章讨论了苏丹I-中性配位体协萃体系萃取分离锂同位素中螯合剂和协萃剂的结构效应。为了获得高的同位素分离效应,螯合剂必须是弱酸性的(PK_α>11),具有强的分子内氢键及易于形成六元螯合环。协萃剂结构不仅要求无空间位阻,而且具有强的配位基。α随配位基的碱性增大而相应提高。萃取络合物中螯合环的增多亦有利于体系α的提高。此外本文还讨论了一些萃取体系的同位素富集方向和萃锂体系用于分离同位素的前景。     

UO_2(HCOO)_2·H_2O在290K-10K的红外光谱及~(235)U-~(238)U同位素位移的研究

本文通过测定甲酸铀酰[UO_2(HCOO)_2·H_2O]在290K-10K的红外光谱,确定了该化合物铀酰基团(O-U-O)v_(as)振动峰位,研究了温度对峰宽、峰位的影响,并采用差减及峰内标法估算了甲酸铀酰在290K-10K的同位素位移值。测得290K,77K及10K时~(238)U的v_(as)值分别为931.90cm~(-1),930.82cm~(-1)和930.74cm~(-1),~(235)U-~(238)U同位素位移△v分别为0.63cm~(-1),0.67±0.18cm~(-1)和0.71±0.21cm~(-1),位移值与理论计算值接近。     

Rapid degradation of the mycotoxin patulin in man quantified by stable isotope dilution assays

The absorption and degradation of the mycotoxin patulin in man was quantified by using a recently developed stable isotope dilution assay. Application of this currently most sensitive method revealed a patulin content less than 200 ng l -1 in the blood serum of five consumers of apple juice. Likewise, no patulin was found in the serum of a volunteer, whose blood was drawn shortly after consumption of a juice containing a maximum tolerable amount of patulin. In further in vitro experiments, the degradation of patulin by reacting it with whole blood was investigated. After addition of 100 μg patulin to 9 ml blood, only 6.1% of the mycotoxin was detected after 2 min. It was concluded, therefore, that even high naturally occurring concentrations of patulin in foods are quickly degraded before reaching other tissues than the gastrointestinal tract.     

RADIOACTIVE OR NATURAL TRACER。TECHNIQUES FOR LEAK DETERMINING OF DAM ABUTMENT

Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes,meanwhile interconnection between boreholes and the energing water points is analysed.The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads.Major single hole techniques including measurement for seepage line,velocity,rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natureal tracers are analysed,uincluding electric-conduct,pH-value and temperature of water as well as stable isotopes(D,^18O) and tritium.Furthermore,the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam.     

Isotope effect and tTc suppression in d-wave superconductors

We have studied the isotope effect on the superconducting transition temperatureT _c ofd-wave pairing instabilities due to antiferromagnetic spin fluctuation exchange. We found that models with conventional coupling toharmonic phonon degrees of freedom and reasonable limits on coupling strength and phonon spectra, give values for the isotope exponent which are at least one order of magnitude smaller than typical observed values of in the cuprates. Models with coupling to non-linear tunneling modes in a stronglyanharmonic multi-well lattice potential and realistic coupling strengths have effectively larger isotopic mass dependences andmay therefore account for the observed magnitudes of.This work was supported by the National Science Foundation (Grant DMR-8913878 and DMR-9215123) and by the University of Georgia Office of the Vice President for Research. Computing support from UCNS, University of Georgia, and NCSA, University of Illinois, is gratefully acknowledged.     

同位素扫描仪的图象信号特点分析及处理方法

分析了同位素扫描仪的图象信号的特点,指出了影响同位素扫描图象质量的主要因素,针对其特点提出了相应的图象处理方法,有效地改善了图象质量。     

塔里木,准噶尔盆地石油生成与演化

以塔里木、准噶尔盆地干酪根、沥青的Ｐｂ、Ｓｒ、Ｎｄ同位素分析资料，回答了地质学家必须回答的四个问题：①石油是由舒什么生成的；②石油是如何生成的；③石油是地何时生成的；④石油是何时运移的。根据Ｐｂ、Ｓｒ、Ｎｄ同位素所揭示的信息指出，塔里木、准噶尔盆地的石油虽然是在不同构造背景下生成的，生油模式、生油年龄和运移年龄也不相同，但都是由费托合成反应无机生成的。作者指出，地救化学急变对油气田分布的控制作用十