离子交换分离和多接收等离子体质谱法高精度测定钛同位素的组成

通过三步离子交换将Ti与地质样品基体分离,并利用多接收等离子体质谱(MC-ICPMS)高精度地测定Ti同位素组成.检查了Al,P Zr,Hf和Nb对Ti同位素测定的干扰情况,确定Al/Ti≤0.05,P/Ti≤0.10,Zr/Ti≤0.01,Hf/Ti≤0.05,Nb/Ti≤0.05的条件下,不影响Ti同位素组成的测定...     

Effect of Lead Contamination on Soil Microbial Activity Measured by Microcalorimetry

Microcalorimetry was used to investigate the microbial activity in three types of soil (orchard soil, crop soil, forest soil) in Wuhan, China, and to evaluate the influence of different concentrations of lead (Pb²⁺) on soil microbial activity. The experimental results revealed that due to different physical and chemical characteristics of the soils, soil microbial activity in three soil samples were in a descending sequence: orchards soil, crops soil, forest soil. Six levels of Pb viz. 0, 10, 20, 40, 80, 160 μg·g⁻¹ were applied in these soils, and the results showed that an increase of the amount of Pb²⁺ is associated with a decrease in microbial activity in the soils due to the toxic effect of Pb²⁺. In order to gain further insight of the sequential change of microorganisms, determination of colony forming units (CFU) was performed to provide a negative linear correlation between the heat effect and the respective number of microorganisms in the system.     

Carbon concentration dependence of the superconducting transition temperature and structure of MgCxNi3

The crystal structure of the superconductor MgC_xNi₃ is reported as a function of carbon concentration determined by powder neutron diffraction. The single-phase perovskite structure was found in only a narrow range of carbon content, 0.88<x<1.0. The superconducting transition temperature was found to decrease systematically with decreasing carbon concentration. The introduction of carbon vacancies has a significant effect on the positions of the Ni atoms. No evidence for long-range magnetic ordering was seen by neutron diffraction for carbon stoichiometries within the perovskite phase stability range.     

Effect of Water Saturation on Pressure-Dependent Permeability of Carboniferous Shale of the Qaidam Basin,China

Permeability is the most important parameter that describes gas flow characteristics in shale. Water saturation and effective pressure have a considerable effect on shale permeability. This paper presents the results of a laboratory study of the effects of water saturation and effective pressure on gas permeability in Carboniferous shales of the Qaidam Basin, China. The permeability of shale samples with varying water saturation (0–33 wt%) was measured at effective pressure of 6.9 to 27.59 MPa and at low mean pore pressure (<?6.89 MPa) at room temperature, using a pressure pulse decay permeameter. The results indicate that the water saturation and the effective pressure are the main factors affecting the shale permeability. Permeability of sample C034, which has a high clay content and is dominated by nanoscale slit-shaped pores, shows a large decrease (up to 90%) with increasing water saturation (from 0 to 31.7 wt%), depending on the effective pressure. A much larger permeability reduction with increasing water saturation fraction is associated with the swelling of clay minerals. For each sample with varying water saturation, our analyses revealed a consistent line relationship between log permeability and effective pressure variation. The impact of effective pressure on the measured permeability becomes more significant as water saturation increases. With increasing water saturation, the gas slippage factor decreases and calculated effective pore size increases, and gas–water flow in the shale samples occurs as channel flow. This study provides practical information for further studies of stress-dependent permeability of shale with water and the gas slippage effect in two-phase, gas–water flow.     

sl(2) variational schemes for solving one class of nonlinear quantum models

Hamiltonians of a wide-spread class of G_inv invariant nonlinear quantum models, including multiboson and frequency conversion ones, are expressed as nonlinear functions of sl(2) generators. This enables us to use variational schemes, based on sl(2) generalized coherent states as trial functions, to obtain new (sl(2) cluster) quasi-classical solutions of spectral and evolution tasks which smoothly approximate exact ones and catch explicitly quantum cooperative features of the models under study (in contrast with standard independent-mode quasi-classical approximations). In such a way new analytical expressions are found for the energy spectra which are beyond both equidistant and quasi-equidistant ones obtained earlier.     

干法灰化-发射光谱法测定植物样品中B和Sn

地球化学样品中的元素硼和锡属于难溶易挥发元素,湿法样品前处理技术相对较难,目前基本以一米光栅发射光谱法测定为主,其固体进样方式避免了复杂的样品前处理,实现了对地球化学样品中元素硼和锡的绿色分析。植物样品经过适宜的高温灰化后,基体成分基本一致,体积质量均发生富集现象,称取的样品灰分成分和基物、缓冲剂(比例1:1:2)经过研磨充分混匀,在优化的实验条件下,以国家一级合成硅酸盐光谱分析标准物质制作校准曲线,构建植物样品中硼和锡的分析方法,该方法硼和锡的检出限分别为0.042μg·g-1、0.019μg·g-1,方法经过国家一级标准物质验证,硼方法精密度:5.6%~13%,正确度(RE)的绝对值均小于10%;锡方法精密度:7.2%~18%,正确度(RE)的绝对值均小于28%。实验结果表明:植物样品经过干法灰化富集后,对植物样品中元素硼基本能够实现精准测定,对元素锡含量接近于检测下限的值测定结果相对较差,对高含量值也能够实现精准测定,方法具有较好的应用价值。