Particle isolation for analysis of uranium minor isotopes in individual particles by secondary ion mass spectrometry

A new technique to measure ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios for individual particles in environmental samples was developed, which was a combination of particle isolation under scanning electron microscope (SEM) and secondary ion mass spectrometry (SIMS). The technique was verified by measuring ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios in individual particles in a simulated environmental sample containing uranium standard (NBL CRM U010) and Pb metal particles. When the uranium particles were not isolated, the relative deviations of the measured isotope ratios from the reference values increased with increasing the signal intensity ratio of ²⁰⁸Pb to ²³⁸U, which was due to the molecular ion interferences by the Pb particles co-existing in the sputtered area. By the isolation of individual uranium particles, the interferences were eliminated and the measured isotope ratios were in good agreement with the reference values. The maximum relative deviations among 20 particles were 8.9% for ²³⁴U/²³⁸U and 13.1% for ²³⁶U/²³⁸U isotope ratios, respectively. The technique was also successfully applied to the analysis of a real swipe sample containing various kinds of elements.     

硅酸盐矿物中低含量元素的电子探针异点分步定量法

以电子探针分析硅酸盐矿物国家标准样品 ,研究了不同分析方法和实验条件对硅酸盐矿物的主量元素和质量分数<2 %的低含量元素的电子探针定量分析精度的影响;结果表明 ,在硅酸盐矿物的电子探针定量分析中 ,在假定不含低含量元素的情况下先用常规实验条件分析主量元素的含量 ,尔后用非常规实验条件异点分析低含量元素的含量 ,并让主量元素参与低含量元素定量计算的ZAF校正 ,可以保证不同含量的被测元素均具有较高的分析精度 ,并称该法为“异点分步定量法”。     

电感耦合等离子体原子发射光谱法测定黄铜中主、次量元素

提出了电感耦合等离子体原子发射光谱法同时测定黄铜中铜和锌等主量元素,镍、铅、铝、锡、铁、锰、磷和钴等次量元素的分析方法。选择了各元素的分析谱线,运用干扰元素系数法校正光谱干扰,用内标校正和同步背景校正消除基体影响。各元素的质量分数均在一定的范围内与其信号强度呈线性关系。方法用于分析两个铜合金样品,测定结果与光电直读光谱法、化学法的测定值一致;用于分析3种铜合金标准样品,测定值与标准值相一致。     

RAS添加剂对富含锡、砷、铅等微量元素灰铸铁内在质量的改善

本文针对龙岩生铁（富含锡、砷、铅等多种微量元素）生产灰铸铁出现的硬、脆、裂等内在 质量问题,在探索性试验的基础上,研制了稀土复合添加剂（ＲＡＳ）对铁水进行处理,使问题得 到较好的解决．文中对处理后的灰铸铁,在显微组织、机械性能（包括质量指标）、铸造性能、 微量元素分布等方面的有关特性,与未经处理的试验结果进行了系统对比。同时,对不同种类处 理剂的效果和ＲＡＳ添加剂的组成也进行了论述．     

An ab initio study of the conformational preferences of Hoechst 33258 in gas-phase and aqueous solution environments

A quantum mechanical study of the conformational preferences of Hoechst 33258, a synthetic minor groove-binding drug, has been performed in both gas-phase and aqueous solution. Gas-phase calculations were performed at the HF/6-31G(d) and MP2/6-31G(d) levels of theory, whereas calculations in the aqueous solution phase were performed using the PCM model with the 6-31G(d) basis set. The molecule was divided into three fragments, which were submitted to a systematic and detailed conformational study. The results clearly indicate that Hoechst 33258 does not adopt a planar conformation in either the gas-phase or aqueous solution. Thus, a folded conformation is not induced by binding of the molecule to DNA, but is an intrinsic property of the compound. Received: 3 March 1998 / Accepted: 29 May 1998 / Published online 19 August 1998     

Metals and phosphorus determination in vegetable seeds used in the production of biodiesel by ICP OES and ICP-MS

Methods for the determination of 5 major (Ca, K, Mg, Na and P) and 14 minor elements (Al, Ba, Cd, Co, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Rb, Sr and Zn) in vegetable seeds by ICP OES and by ICP-MS, respectively, are proposed. After a common sample preparation consisting of smashing and homogenization in an agata mortar, followed by acid digestion in a microwave oven, the diluted sample solutions were measured in the spectrometers using conventional pneumatic nebulizers. External calibration with aqueous standard solutions was used for both techniques. Internal standard was not required, due to the absence of non-spectral interference. For the major elements, the detection limits were in the range of 0.01 (Mg) to 0.3 µg g^− 1 (Na and K) and for the minor elements they were in the range of 0.001 (several) to 0.4 µg g^− 1 (Fe). The detection limits were adequate for the seed analysis. The accuracy was validated by analyzing a botanical certified reference material (Pine Needles). Agreement of the concentrations with the certified or informed values was obtained, according to the t-test for a confidence level of 95%. The relative standard deviations were below 10% indicating an adequate precision. Seeds from seven different plants were analyzed: cotton seed, sunflower, castor bean, fodder turnip, curcas bean, soybean and tung. The element concentrations varied considerably in the different samples. The results were also evaluated using the principal component analysis.     

沉管灌注桩防止颈缩的措施探讨

本文根据临汾地区具有代表性的工程地质对影响灌注桩质量的原因进行了分析,并提出了防止颈缩的措施。     

试析赫梯人进入小亚细亚的途径

印欧种赫梯人迁入小亚细亚的途径主要有两种说法，即高加索说和海峡说。然而，在对高加索山区及周边地区的气候、自然地理环境和古代交通，马的驯化和车辆的发明，以及一些考古材料等进行研究之后，可以认为高加索说更为合理一些。     

微动光栅三维测量仪相移微步距控制系统设计研究

本文根据相移轮廓术的四步相移法设计了微动光栅三维测量仪微步距控制系统,利用单片机AT89C52与3955芯片的接口对3955进行设置和控制,并采用两片3955芯片驱动两相步进电机,实现了电机的微步距控制。系统通过细化步进电机步距角,提高了分辨率和光栅位移精度,满足了每隔四分之一光栅周期进行光栅图像采集的要求,控制系统结构简单,并通过人体模特光栅图像获取实验验证了设计的可行性,完全满足工业及相关三维测量的要求。     

铸造方法对巴氏合金组织及性能的影响

铸造方法对巴氏合金的力学及磨损性能有显著的影响。通过对合金的金相组织观察、相成分的分析,结合磨损试验以及磨损表面形貌分析,研究铸造方法对合金的组织及性能的影响。分析发现离心浇注能明显的细化晶粒,提高合金的耐磨性与减磨性,与静置浇注的合金相比,其磨损量下降了9．6％。