Solid-Phase Extraction and Capillary Gas Chromatographic Determination of Triazine Herbicides in Water

Abstract

A facile and efficient method is described for the determination of trace quantities of triazine herbicides, terbutryn, prometryn and ametryn in water. The procedure involved preconcentration of water samples by sorption on chromatographic grade silica gel particles with chemically modified surface, being covalently bonded with a nonofunctional C₈H₁₇ group. This was followed by solvent desorption with 2-propanol. The determinative step was achieved by capillary gas chromatography on Supelcowax-10 fused silica column using a nitrogen-phosphorus detector. The limit of detection was 0.1 μg-10 μgL^?1.     

Determination of Cadmium and Lead in Sea Water after Extraction Using Electrothermal Atomisation. Minimisation of Interferences from Co-Extracted Sea Salts

Abstract

Interferences from small amounts of sea salt in the determination of cadmium and lead were investigated. Test samples were made to mimic solutions obtained after extraction of sea water for trace metal analysis. Sea salt concentrations in the range 0–400 mg/l were investigated. Background absorption from this salt was high but easily minimised through the addition of nitric acid (2 % v/v). Sensitivity reductions due to the salt were considerable and varied from one graphite tube to the other. This problem was overcome by the addition of 1000 mg lanthanum per litre of sample. The positive effect of the lanthanum matrix modification is thought to be due to a change of the graphite tube surface.     

Deformational Properties of Polymer Concrete during Long-Term Exposure to Water

Changes in the elastic and viscoelastic (creep) characteristics of polymer concrete and its structural components (polyester resin, unfilled or filled with diabase flour) during a long-term exposure to water at 20°C were studied. Modeling the structural changes in polymer concrete with time showed an increase in the relative volume content of pores filled with water and a decrease in that of unfilled pores. Based on the free-volume concept and the data on swelling due to moistening and shrinkage due to physical aging of the binder, a rather accurate estimate of the time-moisture reduction function for polymer concrete was obtained. The function was found to be nonmonotonic: the interval of increase was followed by an interval of decrease.     

重水的冲击压缩性

 用二级轻气炮作为加载装置，测量了重水（D₂O）的冲击压缩线，压力范围为10~43 GPa。用轴对称式电磁感应探头测量冲击波速度，测量精度约1.2%~1.5%。用电探针测量飞片速度，其精度约0.5%。用对比法原理进行测量，标准样品材料为无氧铜。实验发现，重水的冲击波速度随粒子速度变化呈斜率不同的两段直线关系，两线连结处出现拐折。分析认为，这一现象可能由液体D₂O分子在冲击波作用下的离解过程引起。     

GM(1,1)的周期修正模型及其在泉水流量预测中的应用

本文阐述了 GM( 1 ,1 )的残差周期修正模型 ,并将它应用于山西神头泉的流量预测中 ,建立了神头泉流量的 GM( 1 ,1 )周期修正模型 ,对其流量进行了预测 ,为神头泉域岩溶水资源开发利用和保护提供了科学依据     

浅水波方程的一种基于特征方向的Galerkin方法

本文给出求解二维浅水波方程组的一种Crank-Nicolson型基于特征方向的Galerkin有限元方法，证明了该方法的一个误差估计结果，并给出了该方法的一个算例．     

溃坝问题的间断有限元方法

本文研究90年代初提出的Runge-Kutta间断Galerkin有限元方法，给出该方法的精度分析，通过经典算例验证该方法处理间断问题、捕捉锐利波形的能力，并将其推广到求解浅水问题．针对坝底无摩擦，无坡度的理想情形进行讨论，给出方溃坝和圆溃坝问题的数值模拟结果．     

A numerical study of the motion of a wave running up a beach

The main difficulty for the numerical calculation of the wave running up a beach is the treatment of its moving water boundary. In this paper a scheme of turning the free boundary problem into a fixed boundary problem is designed. The calculated run-up height is consistent with the experiments. Some interesting wave phenomena are also found.     

飞秒强激光场中水分子的电离激发

本文运用含时密度泛函理论和分子动力学非绝热耦合的方法, 研究了水分子在不同极化方向的激光场中的电离和动力学行为. 计算结果表明, 对应相同的极化方向, 随着激光强度的增加, 水分子的电离增强; 对于相同强度的激光, 当激光极化方向沿水分子对称轴方向时, 水分子的电离最强, 当激光极化方向垂直水分子对称轴方向时, 水分子电离受到最大程度的抑制. 对水分子偶极矩的研究表明, 当分子处于线性响应区域时, x方向的激光只能激发起x方向的偶极振动而y方向的激光只能激发起y方向的偶极振动. 对水分子的键长和键角的研究表明, 在激光场中水分子的键长变长, 键角变大, 但变化幅度随着激光极化角的增大而减小. 此外, 研究还发现, 虽然在不同极化方向的激光脉冲的驱动下, 水分子OH键的振动频率与激光频率相当, 在脉冲关闭后, 振动频率减小, 但激光场的极化方向对水分子振动模式具有选择性. 关键词： 含时密度泛函理论 分子动力学 水分子 电离