Interference Correction Research Articles

Research on the Inversion Algorithm of Carbon Dioxide Detection By the Non-Dispersive Infrared Technology

Carbon dioxide (CO2) of the automobile exhausts is not only direct atmospheric contaminants, but also contributes to the formation of the greenhouse effect and frequent natural disasters, directly threatening human health and the ecological environment. This work is focused on the monitoring of CO2 by non-dispersive infrared (NDIR) technology. The NDIR instrument is non-poisonous, robust and durable. It has the characteristics of long life, easy maintenance and operation. Accurate measurement of CO2 concentration is very important for monitoring the quality of automobile exhausts. The absorption line of CO2, centered at 4.26μm has been selected due to the very strong absorption peak. The inversion algorithm of CO2 detection is researched in the wide dynamic range of 0-20% for CO2 on NDIR. According to the Beer-Lambert law, the calibration curve are obtained. The least squares method is used to respectively fit the logarithmic function, exponential function, polynomial, etc. to establish three inversion models. After analyzing and verifying these three models, the measurement error is less than 7% in the range of 0-20% for CO2 on NDIR. The results of the experiment shows that three inversion models are effective. They not only overcomes the shortcomings of the detection sensitivity and wide dynamic measurement range on NDIR technology, but also have a good measurement linearity for CO2 detection. They provide a necessary precondition for the interference correction of gas analysis. In addition, this method also provides a solution for the measurement of other gases (such as SO2 and NO2) with high precision and wide dynamic range.

Correction of the moisture variation in wood NIR spectra for species identification using EPO and soft PLS2-DA

The NIRS technology, together with multivariate methods, has already proved to be capable of discriminating wood from different forest species that are visually similar and determining the provenance within the same species. However, models developed with dry wood under controlled conditions of humidity and temperature present prediction errors or high outlier exclusion rates when applied to the analysis of samples under different moisture conditions. This work proposes applying external parameter orthogonalization (EPO) to minimize the effect of moisture in the spectra of wood from native Brazilian species under different moisture conditions and enable its analysis by PLS-DA discrimination models. After correction, the models showed high-efficiency rates and a significant reduction in the number of outliers. For the model trained with oven-dried samples and validated with spectra measured on samples under environment conditions, it was observed that the rate of samples with inconclusive results (RIR) was reduced from 87.8% to 18.4% by using EPO. Under these conditions, efficiency rates of 93.5% were obtained for the identification of Carapa guianensis Aubl. (Andiroba), 98.6% for Swietenia macrophylla King (Mogno) and 100.0% for Cedrela odorata L. (Cedro), Erisma uncinatum Warm. (Cedrinho) and Micropholis melinoniana Pierre (Curupixá). For the second validation set, with samples in more extreme moisture conditions, the same model without EPO correction had a RIR of 100.0%. In comparison the model with EPO had a RIR of 43.8%, demonstrating the feasibility of EPO in the correction of moisture interference in samples under moisture conditions different from those used in the model development. Applying more flexible criteria in the identification of samples by PLS-DA also favored the reduction of errors. Thus, EPO and soft-PLS-DA proved to be an effective strategy to enable the application of NIR technology in field conditions, such as in the inspection of illegal timber trade.

Interferences and Matrix Effects on Iron Isotopic Composition Measurements by 57Fe-58Fe Double-Spike Multi-Collector Inductively Coupled Plasma Mass Spectrometry; the Importance of Calcium and Aluminum Interferences

Multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS) are widely used for Fe isotope measurements. The latter may be perturbed by interferences (notably from Cr and Ni) and matrix effects (notably from major elements), caused by elements remaining in the samples after purification. We quantified some of these perturbations and our ability to correct them whenever possible, using Thermo Neptune and Neptune Plus MC-ICPMS with a 57-58Fe double-spike mass bias correction. 54Cr and 58Ni isobaric interference corrections were found to be extremely efficient up to Cr/Fe=0.12 and Ni/Fe=0.04 (g/g natural Fe). Matrix effects were found negligible up to at least Na/Fe=175, Mg/Fe=10, K/Fe=1.5, and Mo/Fe=75 (g/g natural Fe). 28Si2+ interference was found negligible up to Si/Fe=50. Finally, we found that calcium and aluminum could cause significant interferences (e.g., 40Ca16O and 27Al2+), for Ca/Fe ≥ 2.5 and Al/Fe ≥ 2.5. The perturbation intensity relative to the Ca/Fe ratio was found dependent on the measurement conditions (plateau width). While working with samples with potentially high calcium or aluminum contents (such as calcite minerals or tests, bones and teeth, or marine samples and crustal rocks), we recommend to carefully take into account Ca and Al while tuning the instrument and checking the measurement accuracy with isotopic standards (i.e., doping the isotopic standard with Ca and Al levels comparable to those of the samples).

Single production of vector-like quarks: the effects of large width, interference and NLO corrections

We provide a comprehensive discussion, together with a complete setup for simulations, relevant for the production of a single vector-like quark at hadron colliders. Our predictions include finite width effects, signal-background interference effects and next-to-leading order QCD corrections. We explicitly apply the framework to study the single production of a vector-like quark T with charge 2/3, but the same procedure can be used to analyse the single production of vector-like quarks with charge −4/3, −1/3, 2/3 and 5/3, when the vector-like quark interacts with the Standard Model quarks and electroweak bosons. Moreover, this procedure can be straightforwardly extended to include additional interactions with exotic particles. We provide quantitative results for representative benchmark scenarios characterised by the T mass and width, and we determine the role of the interference terms for a range of masses and widths of phenomenological significance. We additionally describe in detail, both analytically and numerically, a striking feature in the invariant mass distribution appearing only in the T → th channel.

Magnetic field interference correction of high-precision geomagnetic directional technology

Low-cost magnetic and inertial sensors are extensively used for orientation estimation. However, magnetic sensors are very susceptible to environmental disturbance. In order to achieve accurate geomagnetic navigation, appropriate sensor correction procedures must be performed in advance to process measured data correctly. Therefore, a combined correction model and a high-precision geomagnetic directional technology were proposed in this work. Firstly, the working principle of the strapdown three-axis geomagnetic sensor was analyzed, and a unified calibration framework was established. Then, the total least square method (TLS) was utilized to solve all of the error parameters. Finally, a high-precision geomagnetic directional technology was achieved based on the Mahony algorithm. Experimental results revealed that the proposed technology significantly reduces the error amplitude and effectively compensates the data distortion, with higher and more stable compensation accuracy. The results prove the effectiveness of the proposed algorithm and its broad application prospects in military, industrial and civilian fields.

Pseudo isotope dilution (PID) as an approach for correcting barium-related spectral interferences on the measurement of europium by inductively coupled plasma mass spectrometry (ICP-MS)

Pseudo isotope dilution (PID) was suggested as a simple and practical approach for the correction of barium-related spectral interferences on the measurement of europium by inductively coupled plasma mass spectrometry (ICP-MS). The interferents, i.e. oxides and hydroxides of barium, were regarded as pseudo europium isotopes. An equation for calculating the concentration of europium was deduced and the net contribution of europium isotopes can be obtained by measuring the signal intensity ratios of 151I/153I in a sample, a europium standard, and a barium standard, respectively. The validity of the approach was confirmed by the determination of europium in standard solutions with different concentrations of barium. Determination of europium in river water and seawater certified reference materials was carried out, whose results were in coincidence with reference values.

Evaluation of peak-fitting software for magnesium quantification through k0-instrumental neutron activation analysis

The selection and effective utilization of peak-fitting software for conventional gamma-ray spectrum analysis is significant for accurate determination of the mass fraction of elements, particularly in complex peak regions. Majority of the peak-fitting programs can derive similar peak characteristics for singlet peaks, but very few programs can deconvolute multi-peaks in a complex region. The deconvolution of multi-peaks requires special peak-fitting functions, such as left and right-skew distributions. In the this study, 843.76 keV (27Mg) peak area from the complex region (840 keV–850 keV) determined and compared using four different peak-fitting programs, namely, GammaVision, Genie2000, HyperLab, and HyperGam. The 843.76 keV peak interfered with 841.63 keV (152mEu) and 846.81 keV (56Mn). The total Mg concentration was determined through k0-instrumental neutron activation analysis by applying the isotopic interference correction factor 27Al(n,p)27Mg through the simultaneous determination of Al concentration. HyperLab and HyperGam peak-fitting programs reported consistent peak areas, and resultant concentrations agreed with the certified values of matrix-certified reference materials.

Spectral data processing based on maximum noise fraction

The processing of gamma spectrum measurement data has always been an important step in data interpretation of the survey area. It includes the correction of radioactivity interference caused by non-measuring targets, the correction of effects caused by different heights or topography in the survey environment, the smoothness and denoising of the measurement spectrum, etc. The accuracy of each step will affect the final data resources. The interpretation of the materials results in inaccurate regional radioactivity assessment. Maximum noise separation transformation is a similar method to principal component transformation, which is used to reduce dimensionality and noise of data. This paper takes the noise reduction process of gamma spectrum data processing as the research direction, uses SPSS data processing software, combines with MATLAB to denoise the data, and uses the maximum noise separation transformation as the denoising method, applies it to denoise the spectral data, and uses the principal component analysis method and the maximum noise fraction method to denoise the same set of data separately. After analysis, it is concluded that the maximum noise fraction method is superior to principal component analysis when there is a large noise variance for a set of data.

Fourier transform infrared spectroscopy and interference of volatile organic compounds on measurements of methane (CH4) fluxes at tree stems – a general phenomenon for plant systems?

Fourier transform infrared spectroscopy and interference of volatile organic compounds on measurements of methane (CH₄) fluxes at tree stems – a general phenomenon for plant systems?

Nd(III) hypersensitive peak as an optical absorption probe for determining nitric acid in aqueous solution: An application to aqueous raffinate solutions in nuclear reprocessing

A new method using Nd(III) absorption peak as a probe is described for the measurement of nitric acid concentration in aqueous solution. The hypersensitive peak of Nd(III) at 575.1 nm shows a substantial enhancement in the absorbance in comparison to other absorption peaks with increasing nitric acid concentration. The integrated area and absorbance of this hypersensitive peak show a linear dependency over a large dynamic range of 0.5–15.5 M of nitric acid. A methodology for the correction of spectral interference to the probing absorption peak of Nd(III) is also reported. The method is applied for the measurement of nitric acid in synthetic high level liquid waste solution and shown to be comparable to that obtained by titrimetric method. The present method can be easily adopted for the measurement of nitric acid concentration in aqueous raffinate solutions of nuclear reprocessing streams.

LIPIC: An Automated Workflow to Account for Isotopologue-Related Interferences in Electrospray Ionization High-Resolution Mass Spectra of Phospholipids.

In the past decade, hydrophilic interaction liquid chromatography (HILIC) has emerged as an efficient alternative to reversed-phase chromatography (RPC) for the analysis of phospholipid (PL) mixtures based on mass spectrometric detection. Since the separation of PL by HILIC is chiefly based on their headgroup, the mass spectrum of each class can be obtained by spectral averaging under the corresponding HILIC band. Using experimental m/z values resulting from high mass resolution/accuracy instruments, the sum compositions of PL in a specific class can be thus inferred but partial overlapping may occur between signals related to the M + 0 isotopologue of one species and the M + 2/M + 4 isotopologues of species having one/two more C═C bonds in their chemical structures. Here, an automated workflow, named LIPIC (lipid isotopic pattern interference correction), is proposed to account for such interferences. Starting from the experimentally verified assumption that peaks in isotope patterns are Gaussian, LIPIC predicts, as a function of m/z ratio, signal intensities due to M + 2 and M + 4 isotopologues of species with one or two more C = C bonds than the target one and calculates the corrected intensity for the M + 0 isotopologue of the latter. Thanks to an iterative procedure, the suggested algorithm compensates also for slight shifts occurring between experimental and theoretical m/z ratios related to isotopologue peaks. Examples of applications to simulated and experimental mass spectra of two PL classes, i.e., phosphatidylcholines (PC) and cardiolipins (CL), emphasize the increased extent of correction at the increase of molecular masses of involved species.

Effect of proximity-induced spin-orbit coupling in graphene mesoscopic billiards

Van der Waals heterostructures based on two-dimensional materials have recently become a very active topic of research in spintronics, both aiming at a fundamental description of spin dephasing processes in nanostructures and as a potential element in spin-based information processing schemes. Here, we theoretically investigate the magnetoconductance of mesoscopic devices built from graphene proximity-coupled to a high spin-orbit coupling material. Through numerically exact tight-binding simulations, we show that the interfacial breaking of inversion symmetry generates robust weak antilocalization even when the $z\rightarrow -z$ symmetric spin-orbit coupling in the quantum dot dominates over the Bychkov--Rashba interaction. Our findings are in interpreted on the light of random matrix theory, which links the observed behavior of quantum interference corrections to a transition from circular-orthogonal to circular-sympletic ensemble.

Quantifying Global and Random Uncertainties in High Resolution Global Geomagnetic Field Models Used for Directional Drilling

SummaryTotal field strength, declination, and dip angle of the Earth's magnetic field, in conjunction with gravity, are used by magnetic-survey tools to determine a wellbore's location. Magnetic field values may be obtained from global models that, depending on the model, have a wide range of spatial resolution at the Earth's surface from large scale (3000 km) to small scale (28 km). The magnetic field varies continuously in both time and space, so no model can fully capture the complexity of all sources; hence, there are uncertainties associated with the values provided. The SPE Wellbore Positioning Technical Section/Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA) published their original measurement-while-drilling (MWD) error model in 2000. Such models and uncertainties define positional error ellipsoids along the wellbore, which assist the driller in achieving their geological target, in addition to aiding collision avoidance. With the recent update to Revision 5 of the ISCWSA error model, we have reassessed the uncertainties associated with our latest high-resolution global magnetic field model.We describe the derivation of location-specific global and random uncertainties for use with predicted geomagnetic values from high-resolution models within magnetic MWD survey-tool-error models. We propose a sophisticated approach to provide realistic values at different locations around the globe; for example, we determine separate errors for regions where the models have high spatial resolution from aeromagnetic data compared to regions where only satellite data are available.The combined uncertainties are freely available via a web service with which the user can also see how they vary with time. The use of the revised uncertainty values in the MWD-error model, in most cases, reduces the positional error ellipsoids and allows better use of the increased accuracy from recent improvements in geomagnetic modeling. This is demonstrated using the new uncertainty values in the MWD-error model for three standard ISCWSA well profiles. A fourth theoretical well offshore Brazil where the vertical magnetic field is weak shows that with drillstring interference correction relying on the more uncertain magnetic dip, the positional error ellipsoids can increase. This is clearly of concern for attaining geological targets and collision avoidance.

Quantitative WDS compositional mapping using the electron microprobe

Abstract While much progress has been made in electron-probe microanalysis (EPMA) to improve the accuracy of point analysis, the same level of attention has not always been applied to the quantification of wavelength-dispersive spectrometry (WDS) X-ray intensity maps at the individual pixel level. We demonstrate that the same level of rigor applied in traditional point analysis can also be applied to the quantification of pixels in X-ray intensity maps, along with additional acquisition and quantitative processing procedures to further improve accuracy, precision, and mapping throughput. Accordingly, X-ray map quantification should include pixel-level corrections for WDS detector deadtime, corrections for changes in beam current (beam drift), changes in standard intensities (standard drift), high-accuracy removal of background intensities, quantitative matrix corrections, quantitative correction of spectral interferences, and, if required, time-dependent corrections (for beam and/or contamination sensitive materials). The purpose of quantification at the pixel level is to eliminate misinterpretation of intensity artifacts, inherent in raw X-ray intensity signals, that distort the apparent abundance of an element. Major and minor element X-ray signals can contain significant artifacts due to absorption and fluorescence effects. Trace element X-ray signals can contain significant artifacts where phases with different average atomic numbers produce different X-ray continuum (bremsstrahlung) intensities, or where a spectral interference, even an apparently minor one, can produce a false-positive intensity signal. The methods we propose for rigorous pixel quantification require calibration of X-ray intensities on the instrument using standard reference materials, as we already do for point analysis that is then used to quantify multiple X-ray maps, and thus the relative time overhead associated with such pixel-by-pixel quantification is small. Moreover, the absolute time overhead associated with this method is usually less than that required for quantification using manual calibration curve methods while resulting in significantly better accuracy. Applications to geological, synthetic, or engineering materials are numerous as quantitative maps not only show compositional 2D variation of fine-grained or finely zoned structures but also provide very accurate quantitative analysis, with precision approaching that of a single point analysis, when multiple-pixel averaging in compositionally homogeneous domains is utilized.

Influence of Axial Magnetic Interference on Wellbore Position Uncertainty

Accompanied with the widespread application of complex wells such as cluster wells in the exploitation of oil and gas resources, it is becoming more and more important to reduce or accurately describe the size of the wellbore position uncertainty as much as possible. It is well known that axial magnetic interference affects azimuth measurement. In this paper, the correction method of axial magnetic interference in azimuth measurement and uncertainty ellipsoid calculation method considering axial magnetic interference correction are introduced, and the influence of axial magnetic interference correction on the position uncertainty of a horizontal well is analyzed through an example. The research shows that the influence of axial magnetic interference on wellbore position measurement error varies with measurement depth, and axial magnetic interference plays an increasing role in the influence of wellbore position measurement error. Therefore, well trajectory should be measured in an environment free of axial magnetic interference.

How 17O excess in clumped isotope reference-frame materials and ETH standards affects reconstructed temperature

Carbonate clumped isotope measurements (∆47) have been widely applied as a paleothermometer, but various sources of error typically limit their application to anomalies greater than about ±3 °C. Calculation of ∆47 requires a correction for mass interference from 17O, which traditionally assumes all analytes follow a linear relationship between 17O/16O and 18O/16O with a slope of 0.528 and a 17O excess (∆17O) of zero. Here, we evaluate these assumptions by measuring ∆17O in ∆47 reference-frame gases and waters, our mass spectrometer working gas, and ETH standards 1, 2, 3 and 4. We systematically evaluate how the ∆17O of these materials influence ∆47 values, and the magnitude of ∆47 error introduced by assuming a ∆17O of zero. We find most ∆47 reference-frame materials and ETH standards have negative ∆17O values, ranging from −300 to +38 permeg, which can largely be explained by equilibration with surface water at Earth surface temperature. Exceptions include CO2 equilibrated with evaporatively enriched water, which has a more negative ∆17O than other reference-frame materials, and CO2 derived from fossil fuel combustion, which has a less negative ∆17O and greater variance. CO2 heated to 1000 °C in quartz glass tubes shows a small, 5–10 permeg, increase in ∆17O that may reflect contamination in the quartz. CO2 evolved from ETH standards exhibits mean ∆17O values of −151 to −123 permeg, similar to most natural carbonates, but ETH 2 and 4 have greater variance. Our results show that assuming ∆17O = 0 can overestimate or underestimate measured ∆47 values, with the direction of change dependent on whether sample ∆17O falls above or below the ∆17O of the working gas. Similarly, assuming ∆17O = 0 can also overestimate or underestimate ∆47 in the carbon dioxide equilibration scale (CDES), with the direction of change dependent on whether sample ∆17O falls above or below reference-frame materials. The magnitude of this effect is significant, and is equivalent to an error on reconstructed temperature of 0.6–1.7 °C for Earth surface conditions and 1.9–5.8 °C in the shallow crust. While analytical and calibration errors are also important, the effect of ∆17O needs to be considered for ∆47 thermometry to achieve its highest possible accuracy. The same is true for the recently introduced dual clumped isotope thermometer. We provide suggested laboratory protocols that best account for ∆17O when measuring ∆47.

Screening natural product extracts for potential enzyme inhibitors: protocols, and the standardisation of the usage of blanks in \u03b1-amylase, \u03b1-glucosidase and lipase assays

BackgroundEnzyme assays have widespread applications in drug discovery from plants to natural products. The appropriate use of blanks in enzyme assays is important for assay baseline-correction, and the correction of false signals associated with background matrix interferences. However, the blank-correction procedures reported in published literature are highly inconsistent. We investigated the influence of using different types of blanks on the final calculated activity/inhibition results for three enzymes of significance in diabetes and obesity; α-glucosidase, α-amylase, and lipase. This is the first study to examine how different blank-correcting methods affect enzyme assay results. Although assays targeting the above enzymes are common in the literature, there is a scarcity of detailed published protocols. Therefore, we have provided comprehensive, step-by-step protocols for α-glucosidase-, α-amylase- and lipase-inhibition assays that can be performed in 96-well format in a simple, fast, and resource-efficient manner with clear instructions for blank-correction and calculation of results.ResultsIn the three assays analysed here, using only a buffer blank underestimated the enzyme inhibitory potential of the test sample. In the absorbance-based α-glucosidase assay, enzyme inhibition was underestimated when a sample blank was omitted for the coloured plant extracts. Similarly, in the fluorescence-based α-amylase and lipase assays, enzyme inhibition was underestimated when a substrate blank was omitted. For all three assays, method six [Raw Data - (Substrate + Sample Blank)] enabled the correction of interferences due to the buffer, sample, and substrate without double-blanking, and eliminated the need to add substrate to each sample blank.ConclusionThe choice of blanks and blank-correction methods contribute to the variability of assay results and the likelihood of underestimating the enzyme inhibitory potential of a test sample. This highlights the importance of standardising the use of blanks and the reporting of blank-correction procedures in published studies in order to ensure the accuracy and reproducibility of results, and avoid overlooked opportunities in drug discovery research due to inadvertent underestimation of enzyme inhibitory potential of test samples resulting from unsuitable blank-correction. Based on our assessments, we recommend method six [RD − (Su + SaB)] as a suitable method for blank-correction of raw data in enzyme assays.

Accurate correction for the matrix interference on laser ablation MC-ICPMS boron isotope measurements in CaCO3 and silicate matrices

Refinement of the measurement of the boron isotopic composition of carbonate and silicate materials via LA-ICPMS pushes samples size requirements into the range of SIMS (figure redrawn after Foster et al., 2018).

In situ Fe isotopic analyses of fourteen reference materials using a synthetic Cr standard for mass bias and isobaric interference corrections by femtosecond LA-MC-ICP-MS

A new method for the direct determination of Fe isotopic compositions in silicate rock samples by fs LA-MC-ICP-MS.

Precise δ88/86Sr determination on a MC-ICP-MS by an improved method combining Zr-empirical external normalization isobaric interference correction and 84Sr–87Sr double spike

Zr-EEN isobaric interference correction coupled with the 84Sr–87Sr double spike method allows highly accurate and precise δ88/86Sr determination on a MC-ICP-MS.