Behavior of the continuous X-ray background in grazing-exit electron probe X-ray microanalysis

The energy distribution of the background radiation originating from two kinds of substrate materials has been studied using Electron Probe X-Ray Microanalysis (EPMA) at grazing-exit angles. The different behavior between tendencies of background reduction for the silicon and the gold substrates at the grazing exit angle is explained using a critical energy concept. It is also shown experimentally that a gold substrate results in a lower background intensity than a silicon substrate in the energy region 5–7 keV, while on the other hand, for elements with X-ray lines of 2–3 keV, it is advantageous to perform the analysis when such elements are deposited on the silicon substrate.     

A maximum information utilization approach in X-ray fluorescence analysis

X-ray fluorescence data bases have significant contradictions, and inconsistencies. We have identified that the main source of the contradictions, after the human factors, is rooted in the signal processing approaches. We have developed signal processors to overcome many of the problems by maximizing the information available to the analyst. These non-paralyzable, fully digital signal processors have yielded improved resolution, line shape, tailing and pile up recognition. The signal processors account for and register all events, sorting them into two spectra, one spectrum for the desirable or accepted events, and one spectrum for the rejected events. The information contained in the rejected spectrum is mandatory to have control over the measurement and to make a proper accounting and allocation of the events. It has established the basis for the application of the fundamental parameter method approach. A fundamental parameter program was also developed. The primary X-ray line shape (Lorentzian) is convoluted with a system line shape (Gaussian) and corrected for the sample material absorption, X-ray absorbers and detector efficiency. The peaks also can have, a lower and upper energy side tailing, including the physical interaction based long range functions. It also employs a peak and continuum pile up and can handle layered samples of up to five layers. The application of a fundamental parameter method demands the proper equipment characterization. We have also developed an inverse fundamental parameter method software package for equipment characterisation. The program calculates the excitation function at the sample position and the detector efficiency, supplying an internally consistent system.     

Assessing the size-dependent chemical speciation of soil particles using electron probe X-ray microanalysis

Soils of the Pereemnaya river catchment, East Siberia, Russia, characterized by high percentage of particles under 10 μm size and the almost total absence of clay minerals, were studied using ultra-thin window electron probe X-ray microanalysis (EPMA). Three subfractions – 10–5 μm, 1–5 μm and <1 μm were distinguished within <10 μm fraction on the basis of mineralogical composition and chemistry peculiarities. Besides the single particles characterization, the bulk chemistry of specified subfractions and their contributions to the bulk soil chemistry were evaluated. It was shown that concentrations of alkali and alkaline-earth metals within <10 μm fraction increased in the row (5–10 μm) < (1–5 μm) < (<1 μm). The presence of two mica types – low-Fe and rich-Fe – was detected in all the subfractions. Being compared with the soil bulk chemistry, the data obtained for fraction <10 μm show that this fraction is the major source of alkali and alkaline-earth metals and consequently the main contributor to element release due to weathering.     

Study on the influence of X-ray tube spectral distribution on the analysis of bulk samples and thin films: Fundamental parameters method and theoretical coefficient algorithms

Knowledge of X-ray tube spectral distribution is necessary in theoretical methods of matrix correction, i.e. in both fundamental parameter (FP) methods and theoretical influence coefficient algorithms. Thus, the influence of X-ray tube distribution on the accuracy of the analysis of thin films and bulk samples is presented. The calculations are performed using experimental X-ray tube spectra taken from the literature and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al. (X-Ray Spectrom. 14 (1985) 125–135), Ebel (X-Ray Spectrom. 28 (1999) 255–266), and Finkelshtein and Pavlova (X-Ray Spectrom. 28 (1999) 27–32). In this study, Fe–Cr–Ni system is selected as an example and the calculations are performed for X-ray tubes commonly applied in X-ray fluorescence analysis (XRF), i.e., Cr, Mo, Rh and W. The influence of X-ray tube spectra on FP analysis is evaluated when quantification is performed using various types of calibration samples. FP analysis of bulk samples is performed using pure-element bulk standards and multielement bulk standards similar to the analyzed material, whereas for FP analysis of thin films, the bulk and thin pure-element standards are used. For the evaluation of the influence of X-ray tube spectra on XRF analysis performed by theoretical influence coefficient methods, two algorithms for bulk samples are selected, i.e. Claisse–Quintin (Can. Spectrosc. 12 (1967) 129–134) and COLA algorithms (G.R. Lachance, Paper Presented at the International Conference on Industrial Inorganic Elemental Analysis, Metz, France, June 3, 1981) and two algorithms (constant and linear coefficients) for thin films recently proposed by Sitko (X-Ray Spectrom. 37 (2008) 265–272).     

Utilising spatial frequency filtering to extract nanoscale layer structure information from isotropic small-angle X-ray scattering data

 A separation method by spatial frequency filtering of the diffuse background of small-angle X-ray scattering (SAXS) is transferred to the case of isotropically scattering samples of polymer materials. Analysis of the residual discrete SAXS is demonstrated. Evaluations of model scattering curves from lamellar two-phase systems show that this technique, in general, results in a good separation. If samples with pure particle scattering or such with rough domain surfaces are investigated, the separation of a suitable background is possible, but is prone to some uncertainty which is estimated. In the case of particle scattering from lamellae the problem is solved by fitting a model function considering polydispersity to the Lorentz-corrected scattering intensity. After background correction the residual information on the distorted nanostructure is collected in an interface distribution function, from which topological parameters can be recovered with high accuracy. These parameters comprise average layer thicknesses and parameters of particle polydispersity. Parameter recovery is achieved by nonlinear regression with model functions describing stacking statistics. Automated versions of the technique are suited to process and analyse series of polymers collected in time-resolved synchrotron radiation experiments. Received: 24 July 2001 Accepted: 12 September 2001     

Considerations in the determination of orientational order parameters from X-ray scattering experiments

An assessment of the data processing and analysis methods used to obtain the second- and fourth-rank orientational order parameters of liquid crystals from X-ray scattering experiments has been carried out, using experimental data from four extensively studied alkyl-cyanobiphenyls and calculated data generated from two general types of theoretical orientational distribution function. The application of a background subtraction and two different baseline correction methods to the scattering profiles is assessed, along with three different methods to analyse the processed data. The choice of baseline correction method is shown to have a significant effect: an offset to zero overestimates the order parameters from the experimental and calculated data sets, particularly for lower order parameters arising from broad distributions, whereas an offset to a value estimated from regions of low scattering intensity provides experimental values close to those reported from other experimental techniques. By contrast, the three different analysis methods are shown generally to result in relatively small absolute differences between the order parameters. We outline a straightforward general approach to experimental X-ray scattering data processing and analysis for uniaxial phases that results in order parameters that match well with those reported using other experimental techniques.     

X射线荧光光谱法测定Zn镀层质量厚度及计算谱线选择问题研究

用X射线荧光光谱法测定了Fe基上Zn镀层的质量厚度；研究了厚度不同时选用不同谱线计算对测定结果的影响，发现在镀层质量厚度较小时（约〈14mg／cm^2）测量Zn元素的Kα线，质量厚度较大时选择Zn的Kα和Fe的Kα线共同计算，用纯元素和相似标样校正测定结果之间的偏差最小；用纯元素作校正标样测定了3个标准样品的Zn镀层质量厚度，计算结果与标准值符舍得较好。     

补偿效应研究的一个新视角

补偿效应与Arrhenius方程关系密切。本文为补偿效应研究提供了新视野。用几何图象分析了Arrhenius方程,指出过去认为此方程只表示速率与温度关系是不全面的,忽视了速率常数与活化能关系的研究。从图形看出,指前因子与活化能本身就具有互补关系,虽仅限于每两个不同活化能的情况。反应是一自组织过程。补偿效应的成立有必要条件和充分条件。欲实现补偿效应,从协同学角度考虑,E/T作为参变量必需小于一阈值,以使反应起活。并有一自变量做系列改变,以使A、E随其相似地连续变化,从而连通所有A、E的内在联系,1/T-lnk图中诸直线交于一点。指数分布是非均匀体系最具有普遍意义的分布函数。概率分析指出,补偿效应是A、E在固体表面和内部均呈相似指数分布的产物。对催化反应与非催化反应有普适性。在速率常数中体现为结构分布概率因子及能量分布概率因子。     

基本参数法在能量色散X射线荧光分析金属样品中的应用

在X射线荧光分析中,基本参数法是校正元素间吸收增强效应的数学方法之一。我们使用带有不锈钢窗的~(241)Am59.6keVγ射线作为激发源,用Si(Li)半导体探测器和多道脉冲幅度分析器作为实验手段。采用无标样法,即绝对测量法,因而具有更大的广泛性和实用性。实验中,我们除了考虑元素间的二次、三次荧光吸收增强作用外,对样品中元素     

Determination of the orientation distribution function of anisotropic paramagnetic species from the angular dependence of the ESR spectra

A method for determination of the orientation distribution function of anisotropic paramagnetic species from the angular dependence of the ESR spectra based on simulation of the spectra was developed. The orientation distribution function is represented as a sum of orthonormal functions. The weight coefficients are determined by minimizing the deviations of the theoretical spectra from experimental ones. The method was numerically tested. The method is relatively insensitive to the presence of noise and foreign ESR signals not related to the sample orientation in the magnetic field.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2595–2601, December, 2004.     

返回拟制探寻法思维的逻辑起点

法思维逻辑起点的模糊,已成为推进法治建设的观念障碍。遵循逻辑规则是法律思维的显著特征。为法治服务的法思维,其逻辑起点是拟制的法律。法律规范的内容虽源自社会,但体系性的法律架构是立法者拟制的产物。被拟制的法律原则、规范、概念、主体等作为制度性事实是“效果历史”的组成部分。作为意向思维的结果,法律对所欲调整的社会已有所定义。法治是由法律定义的秩序。法律既是思维的指引,也是推理的前提、解释的对象、论证的依据。法律思维的基本特征是“据法思考”,拟制的法律是据法思考的逻辑起点。     

Determination of the concentration profile of interfaces in multilayered nanostructures according to the angular dependence of X-ray photoelectron spectra: A new approach

The possibility of determining the concentration profile of interfaces in multilayered nanoheterostructures according to the data of the angular dependence of X-ray photoelectron spectra was shown. To solve this ill-posed inverse problem, we used Tikhonov’s regularization method with iterative refinement. To determine the optimum parameter of regularization, we used the L curve technique. The programs used for this study allowed high accuracy of calculations. All this made it possible to obtain information about the distribution of atoms of a definite sort with a resolution of 0.1–0.15 nm in depth. The results of numerical simulation of XPS spectra are given for a three-layered Cr/Fe structure. Solving the inverse problem for the initial data distorted by the statistical noise afforded a concentration distribution over depth for Cr and Fe atoms. The stability of the solution against experimental errors was determined.     

Study of the Linear Range in HPLC Analyses with UV Detection: Methodology and Experimental Application to the Influence of the Analyte UV Spectrum

Determination of the linear range is one of the main concerns in validation of an HPLC analysis method. It is particularly important since single point calibration will be then used routinely. We proposed an iterative methodology to handle this problem. The idea was, at each step, to test statistically whether the following point belonged to the same regression line. The methodology was then used to evaluate quantitatively the effect on linear range of a shift in detection wavelength or of the detector bandwidth. Although experimental results were globally in accordance with spectroscopic theory, magnitudes observed were rather large. So the linear range could vary by a factor of over 2 with changes in conditions that remained within the range of current practical values. Changes in detection wavelength were limited to about fifteen nm around λ_max and the detector used was considered to be representative of modern high-performance UV detectors. The question of how to take consequences in method validation into account was raised. The solution proposed recommended that the validation was undertaken in conditions as close as possible to those where the method would be conducted routinely. This means with the same instrumentation and on the product of interest for analyses.     

Application of Lie algebraic method to the calculation of rotational spectra for linear triatomic molecules

The Hamiltonian describing rotational spectra of linear triatomic molecules has been derived by using the dynamical Lie algebra of symmetry group U1(4) U2(4). After rovibrational interactions being considered, the eigenvalue expression of the Hamiltonian has the form of term value equation commonly used in spectrum analysis. The molecular rotational constants can be obtained by using the expression and fitting it to the observed lines. As an example, the rotational levels of v2 band for transition (02°0-0110) of molecules N2O and HCN have been fitted and the fitting root-mean-square errors (RMS) are 0.00001 and 0.0014 cm-1, respectively.     

二种求算晶体平面间距d_(hkl)的数学方法

用数学方法推导出结构化学晶体学中晶面间距的一般通式,并在此基础上推导出其他晶系的晶面间距(d(hkl))的计算表达式。     

An application of derivative and continuous wavelet transforms to the overlapping ratio spectra for the quantitative multiresolution of a ternary mixture of paracetamol, acetylsalicylic acid and caffeine in tablets

Quantitative multiresolution of tablets and ternary mixtures of paracetamol (PAR), acetylsalicylic acid (ASP) and caffeine (CAF) having strongly overlapping spectra was accomplished by two graphical transform methods as ratio spectra first derivative-zero crossing and ratio spectra-continuous wavelet transform-zero crossing (ratio spectra CWT-zero crossing) methods. In this study, ratio spectra derivative-zero crossing and ratio spectra CWT-zero crossing methods are based on the use of transformed signals of the ratio spectra and their calibration graphs were obtained by measuring the dA/dλ and CWT amplitudes of the ratio spectra corresponding to zero crossing points. For the comparison purpose, PLS calibration method was applied to predict the content of the same mixtures containing the subject active compounds. The obtained calibrations were tested by using the synthetic mixtures and standard addition technique and they applied to the simultaneous determination of PAR, ASP and CAF in commercial pharmaceutical preparation. The obtained results were statistically compared with each other as well as those obtained by HPLC method and they showed good agreement.     

A simple approach to treat anisotropic elastic collisions in Monte Carlo calculations of the electron energy distribution function in cold plasmas

A simplified method allowing one to treat anisotropic electron heavy species elastic scattering in MonteCarlo models of gas discharges with the proper value for collision frequency is proposed The method is applied to an electric discharge in a Ne · Xe/HCl mixture, and the results are compared with the solution of the two-term expansion of the Boltzmann equation under the same conditions. Methods for reduction of computational time in Monte Carlo codes and the use of the Monte Carlo flux method are also discussed.