Colle-Salvetti-type correction for electron-nucleus correlation in the nuclear orbital plus molecular orbital theory

A Colle-Salvetti (CS)-type electron-nucleus correction in the nuclear orbital plus molecular orbital theory is proposed. The CS-type correction is designed to satisfy the cusp condition for the electron-nucleus interaction. Since the CS-type correction is expressed in terms of the electron and nucleus densities, its evaluation is computationally feasible. Numerical assessment confirms that the CS-type correction performs well for the small G2 set.     

Pile-Up Correction for Improved Accuracy and Speed of X-Ray Analysis

Despite advances in electronic design, pile-up artefacts are still common in EDX spectra and can lead to false element identifications, inaccurate correction for peak overlap and losses of counts that give poor quantitative results. With the capability to do spectrum imaging there is increasing temptation to work at count rates far beyond the correction capability of pile-up inspection electronics. Fundamental limitations due to noise are explained and a new correction procedure is described that implements a comprehensive channel-by-channel correction for pile-up. Practical examples are given that demonstrate the range of application of the new algorithm and show that, with correction, count rates at least 4 times higher can be used with no sacrifice in performance.     

Correction method for quantitative area determination of overlapping chromatographic peaks based on the exponentially modified Gaussian (EMG) model

A simple method is presented for peak area correction of overlapping peaks. This correction is necessary for the normal approach of dealing with overlapping peaks by a vertical line at the valley point. The relative area errors caused by this vertical line are calculated as the correction factors in three dimensions of peak separation, peak ratio, and peak tailing skew. The calculation is based on the exponentially modified Gaussian asymmetric peak model.     

The determination of chromium, copper and nickel in groundwater using axial plasma inductively coupled plasma atomic emission spectrometry and proportional correction matrix effect reduction

The performance of a proportional correction matrix effect reduction procedure was investigated for an axially viewed inductively coupled plasma. It was shown that the proportional correction factor (ratio of analyte matrix effect and internal standard matrix effect) was sufficiently stable over the investigated matrix element concentration ranges (0–2000 mg/L of Na and 0–400 mg/L of Ca) for the procedure to be successful. Proportional correction results in the best correction for matrix effects compared to the classical 1?:?1 intensity ratio correction procedure or the approach without any correction, as was shown in recovery experiments using analyte spiked groundwater samples. Matrix effects as high as 18% without correction were reduced to less than 4% applying proportional correction.     

Corrections for matrix effects in X-ray fluorescence analysis—A tutorial

This paper presents the basic concepts of the mathematical correction for matrix effects in X-ray fluorescence analysis. The emphasis is placed on the correction factor for matrix effects and its quantification. This correction factor is calculated using mathematical models proposed by Lachance–Traill, Claisse–Quintin and Rousseau, which can be applied in practice via an efficient calibration procedure. Each variable in these models is clearly identified so that specific numerical values can easily be substituted for calculation. This paper describes and emphasizes the application of the most effective existing models.     

氢气在热导检测器上的相对校正因子

用三种不同来源的标准气，当实验测定了氮气作载气时，以甲烷作标准物，氢气在热导检测器上的相对摩尔校正因子值为０．２１０ 和相对质量校正因子值为０．０２６４。测定误差小于５％ 。该测定值可供天然气和化工行业气体分析工作者参考。     

荧光光谱的罗丹明B校正原理

一般荧光光谱仪推荐的校正方法是罗丹明B法,但仪器说明书对该方法的原理没有介绍。本文通过研究不同浓度罗丹明B溶液的激发光谱、发射光谱和吸收光谱再结合理论分析阐明了罗丹明B浓溶液可作为量子计数器的原因及其校正光谱的原理。     

Computation of methodology-independent single-ion solvation properties from molecular simulations. III. Correction terms for the solvation free energies, enthalpies, entropies, heat capacities, volumes, compressibilities, and expansivities of solvated ions

The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions (finite or periodic system, system or box size) and treatment of electrostatic interactions (Coulombic, lattice-sum, or cutoff-based) used during these simulations. However, as shown by Kastenholz and Hu?nenberger [J. Chem. Phys. 124, 224501 (2006)], correction terms can be derived for the effects of: (A) an incorrect solvent polarization around the ion and an incomplete or/and inexact interaction of the ion with the polarized solvent due to the use of an approximate (not strictly Coulombic) electrostatic scheme; (B) the finite-size or artificial periodicity of the simulated system; (C) an improper summation scheme to evaluate the potential at the ion site, and the possible presence of a polarized air-liquid interface or of a constraint of vanishing average electrostatic potential in the simulated system; and (D) an inaccurate dielectric permittivity of the employed solvent model. Comparison with standard experimental data also requires the inclusion of appropriate cavity-formation and standard-state correction terms. In the present study, this correction scheme is extended by: (i) providing simple approximate analytical expressions (empirically-fitted) for the correction terms that were evaluated numerically in the above scheme (continuum-electrostatics calculations); (ii) providing correction terms for derivative thermodynamic single-ion solvation properties (and corresponding partial molar variables in solution), namely, the enthalpy, entropy, isobaric heat capacity, volume, isothermal compressibility, and isobaric expansivity (including appropriate standard-state correction terms). The ability of the correction scheme to produce methodology-independent single-ion solvation free energies based on atomistic simulations is tested in the case of Na(+) hydration, and the nature and magnitude of the correction terms for derivative thermodynamic properties is assessed numerically.     

Self-consistent empirical correction for matrix effects in X-ray analysis

An empirical method for generating correction factors for X-ray attenuation due to particle size and matrix effect is described. The method uses two targets of the same material to measure attenuation, and from the ratios of the X-rays, the true values can be derived. The experiments were made on Unites States Geological Standards excited by an X-ray tube with a molybdenum anode. They confirm the efficiency of the proposed new technique for matrix correction. The accuracy achieved by the proposed self-consistent empirical correction is about ∼4%, corresponding to ∼20% for the same samples without correction. The main part of this work was done in Crocker Nuclear Laboratory, Physics Department, University of California Davis, Calif., USA.     

First-order gradient correction for the exchange-energy density functional for atoms

Summary Spurred by earlier discoveries by Deb and others that a first-order correction in the kinetic energy functional leads to an improved kinetic energy, a first-order gradient term is studied as a component of the gradient-corrected functional for atomic exchange energy. This term is shown to improve the local density approximation to the exchange energy more than does the usual second-order gradient correction. The imperative of systematically deriving this gradient correction is discussed but not resolved.     

Systematic errors in the measurement of heat by flow microcalorimetry

It is shown that a number of systematic errors must be considered when performing heat measurements by flow microcalorimetry because the nature of the flow technique is such that substantial heat loss can be incurred. The conventional procedure of electrical calibration is found to be an inadequate correction parameter. Equations to account for the effects of thermal disequilibrium are derived from the basic principles incorporated in the Tian equation. The predicted relationships are tested by simple experiments and shown to be correct. The various correction parameters are measured for a wide range of flow rate and heat input conditions. A composite equation is presented which allows for the correction of heat loss while deconvoluting electrical heat from a heat of reaction. The total heat output rate from a flow calorimeter can be calculated for most experimental conditions by reference to this equation and to the tabulated correction values.     

The determination of chromium, copper and nickel in groundwater using axial plasma inductively coupled plasma atomic emission spectrometry and proportional correction matrix effect reduction

The performance of a proportional correction matrix effect reduction procedure was investigated for an axially viewed inductively coupled plasma. It was shown that the proportional correction factor (ratio of analyte matrix effect and internal standard matrix effect) was sufficiently stable over the investigated matrix element concentration ranges (0–2000 mg/L of Na and 0–400 mg/L of Ca) for the procedure to be successful. Proportional correction results in the best correction for matrix effects compared to the classical 1 : 1 intensity ratio correction procedure or the approach without any correction, as was shown in recovery experiments using analyte spiked groundwater samples. Matrix effects as high as 18% without correction were reduced to less than 4% applying proportional correction. Received: 22 February 1997 / Revised: 28 May 1997 / Accepted: 7 June 1997     

Ab initio molecular dynamics study of water at constant pressure using converged basis sets and empirical dispersion corrections

It is generally believed that studies of liquid water using the generalized gradient approximation to density functional theory require dispersion corrections in order to obtain reasonably accurate structural and dynamical properties. Here, we report on an ab initio molecular dynamics study of water in the isothermal-isobaric ensemble using a converged discrete variable representation basis set and an empirical dispersion correction due to Grimme [J. Comp. Chem. 27, 1787 (2006)]. At 300 K and an applied pressure of 1 bar, the density obtained without dispersion corrections is approximately 0.92?g/cm(3) while that obtained with dispersion corrections is 1.07 g/cm(3), indicating that the empirical dispersion correction overestimates the density by almost as much as it is underestimated without the correction for this converged basis. Radial distribution functions exhibit a loss of structure in the second solvation shell. Comparison of our results with other studies using the same empirical correction suggests the cause of the discrepancy: the Grimme dispersion correction is parameterized for use with a particular basis set; this parameterization is sensitive to this choice and, therefore, is not transferable to other basis sets.     

碱消解-火焰原子吸收光谱法测定土壤中六价铬

建立了碱消解-火焰原子吸收光谱法测定土壤中六价铬的方法。讨论了pH值对六价铬测定的影响。干扰实验的结果表明同等含量的三价铬对六价铬测定无干扰。实验对比了无背景校正、氘灯背景校正、塞曼背景校正三种工作方式,分别对低、中、高三个水平土壤六价铬标准物质进行了测定,结果表明,低含量的土壤样品用塞曼背景校正方式测定的结果更准确,最终选择了塞曼背景校正的工作方式。方法的线性范围0.1～2.0mg/L,线性相关系数R为0.999 8,相对标准偏差(RSD)为1.1%;当取样量5g,定容体积100mL时,方法检出限为0.20mg/kg,加标回收率为84.8%～86.9%,能满足日常测定需求。     

Use of maximum temperature for correction of alanine dosimetry in electron beams

Alanine dosimetry is well characterized for irradiation temperature response. In use, alanine absorbed dose response is corrected for the irradiation temperature. The temperature used to correct alanine dosimetry absorbed dose response in electron beams has historically been the mean temperature occurring during irradiation (Sharpe and Miller, 2009). At lower absorbed doses, the change in temperature is relatively low; thus the absorbed dose response correction due to temperature is small. However, industrial electron beam processing often requires higher absorbed dose measurements where the change in temperature can be very large and the corresponding dose response correction for alanine becomes significant. This paper compares the impact of the temperature correction based on the use of a mean irradiation temperature (Sharpe and Miller, 2009) versus the use of a maximum irradiation temperature on the absorbed dose measurement. The results of this comparison indicate that the use of a mean temperature correction for higher absorbed doses measured with temperature corrected alanine dosimetry introduces a bias in the absorbed dose estimate.     

A fully automated iterative moving averaging (AIMA) technique for baseline correction

Baseline correction is one of the pre-processing steps in the analysis of metabolite signals from chemometric analytical instruments. Fully automated baseline correction techniques, although more convenient to use, tend to be less accurate than semi-automated baseline correction. A fully automated baseline correction algorithm, the automated iterative moving averaging algorithm (AIMA), is presented and compared with three recently introduced semi-automated algorithms, namely the adaptive iteratively reweighted penalized least squares (airPLS), Asymmetric Least Squares baseline correction (ALS) and a parametric method, using NMR, Raman and HPLC chromatograms. AIMA's potential in increasing the accuracy of multivariate analysis via SELTI-TOF and LCMS chromatograms was also assessed. The results show that the AIMA's accuracy is comparable to these semi-automated algorithms and has the advantage of ease of use. An AIMA plug-in for an open source metabolomics analysis tool, MZmine, was also developed. The AIMA plug-in is available at http://padel.nus.edu.sg/software/padelaima.     

Characterization of municipal solid waste incineration (MSWI) bottom ash by scanning electron microscopy and quantitative energy dispersive X-ray microanalysis (SEM/EDX)

Scanning electron microscopy (SEM) with energy-dispersive X-ray microanalysis (EDX) is frequently used for morphological and qualitative chemical characterization of different materials. The applicability of this method for phase identification, is, however, often underestimated. The application of SEM/EDX for the characterization of different phases in fresh and altered municipal-waste incinerator bottom-ash samples with high lateral resolution is presented. Polished thin sections were prepared from the samples, but fresh fracture surfaces were also used. The EDX analyses were performed by using the correction procedures of a conventional standardless ZAF correction, a peak-to-background ZAF correction, and a correction method for light-element analysis. Because of their highly reactive properties the bottom-ash SEM samples require a special method of preparation. The method facilitates nondestructive preparation of the sensitive bottom-ash alteration phases (e.g. cement phases, hydroxides, salts) and their microstructures.     

Correction to constrained coupled cluster doubles models based on the second coupled cluster central moment

We develop a correction for the coupled cluster version of the perfect pairing (PP) model. The correction is based on finding modified values of the PP amplitudes such that the second coupled cluster central moment defined in the space of all valence single and double substitutions vanishes and, subject to this constraint, minimizing the deviation between the modified and unmodified PP amplitudes with respect to a chosen metric. We discuss how this correction can be generalized to other constrained doubles models, such as local correlation and active-space models. While the correction is not strictly size consistent and retains some of the deficiencies of the PP model, numerical results indicate that much of the missing active-space coupled cluster singles and doubles correlation energy is recovered.     

Gamma-ray spectrometry for the self-attenuation correction factor of the sand samples from Antalya in Turkey

In this paper, we attempt to determine the self-attenuation correction factor for 37 different sand samples collected from Antalya region of Turkey with densities changing from 2.205 to 2.679 g  \(\hbox {cm}^{-3}.\) Transmission method has been used in order to obtain self-attenuation correction factor in comparison with the air and ultrapure water samples for each case. Self-attenuation correction factor versus energy fit curve is obtained. While the self-attenuation correction factor has large values at low energies, it becomes smaller at high energies and tends to become constant thereafter.