Standard Calibration Techniques Research Articles

Novel plenoptic Imager for 3D Particle Tracking Velocimetry for Fluid Structure Interactions

We show a novel plenoptic camera architecture and demonstrate its ability to perform three-dimensional three-component velocimetry using standard multi camera processing techniques. The novel architecture needs only a custom lens assembly with no modification to the camera body. This allows the use of any camera with an appropriate sensor size. The architecture directly creates multiple views of a scene side by side on the camera sensor which can be separated and treated as if they originated from independent cameras. Standard calibration techniques for creating 3D to 2D correspondence on the images can then be implemented to reconstruct 3D scene information. For this case we focus on performing 3D PTV using the commercial software DaVis and the "shake-the-box" algorithm. We look at the flow induced by an oscillating rod and compare the results with the analytical solution to validate the results.

Kalman filtering approach to polarimetric calibration of an optical imager

The Mueller matrix of an optical instrument describes the polarimetric effects the instrument will have on the optical observations it makes in terms of the Stokes parameters. The calibration of the instrument relies on a robust characterization of the elements of this matrix. In this paper, we present what we believe is a new technique that uses Kalman filtering to characterize the Mueller matrices of optical instrumentation based on a set of lab calibration measurements. Kalman filtering is a ubiquitous statistical optimizer that works by comparing measurements and a model of the observed physical system to minimize error. Typically, this technique is applied as a filter to refine a set of observations, but it can also be used to retrieve the properties of the physical system that are not directly measured. We demonstrate the use of the Kalman approach to polarimetric calibration through simulation of measurements, where the polarimetric behavior of optical elements is represented by the Mueller matrices of individual components. The elements of these Mueller matrices are then retrieved with the uncertainty estimates using the Kalman filter approach. The results of this simulation are compared to the standard polarimetric calibration technique as a benchmark, demonstrating the superior performance of the Kalman approach. Then, both the Kalman technique and the standard technique are applied to real measurements from a multispectral polarimetric imager used for atmospheric aerosol remote sensing.

High-fidelity and polarization-insensitive universal photonic processors fabricated by femtosecond laser writing

Abstract Universal photonic processors (UPPs) are fully programmable photonic integrated circuits that are key components in quantum photonics. With this work, we present a novel platform for the realization of low-loss, low-power, and high-fidelity UPPs based on femtosecond laser writing (FLW) and compatible with a large wavelength spectrum. In fact, we demonstrate different UPPs, tailored for operation at 785 nm and 1550 nm, providing similar high-level performances. Moreover, we show that standard calibration techniques applied to FLW-UPPs result in Haar random polarization-insensitive photonic transformations implemented with average amplitude fidelity as high as 0.9979 at 785 nm (0.9970 at 1550 nm), with the possibility of increasing the fidelity over 0.9990 thanks to novel optimization algorithms. Besides being the first demonstrations of polarization-insensitive UPPs, these devices show the highest level of control and reconfigurability ever reported for a FLW circuit. These qualities will be greatly beneficial to applications in quantum information processing.

Field evaluation of semi-automated moisture estimation from geophysics using machine learning.

Geophysical methods can provide three-dimensional (3D), spatially continuous estimates of soil moisture. However, point-to-point comparisons of geophysical properties to measure soil moisture data are frequently unsatisfactory, resulting in geophysics being used for qualitative purposes only. This is because (1) geophysics requires models that relate geophysical signals to soil moisture, (2) geophysical methods have potential uncertainties resulting from smoothing and artifacts introduced from processing and inversion, and (3) results from multiple geophysical methods are not easily combined within a single soil moisture estimation framework. To investigate these potential limitations, an irrigation experiment was performed wherein soil moisture was monitored through time, and several surface geophysical datasets indirectly sensitive to soil moisture were collected before and after irrigation: ground penetrating radar, electrical resistivity tomography (ERT), and frequency domain electromagnetics (FDEM). Data were exported in both raw and processed form, and then snapped to a common 3D grid to facilitate moisture prediction by standard calibration techniques, multivariate regression, and machine learning. A combination of inverted ERT data, raw FDEM, and inverted FDEM data was most informative for predicting soil moisture using a random regression forest model (one-thousand 60/40 training/test cross-validation folds produced root mean squared errors ranging from 0.025-0.046 cm3/cm3). This cross-validated model was further supported by a separate evaluation using a test set from a physically separate portion of the study area. Machine learning was conducive to a semi-automated model-selection process that could be used for other sites and datasets to locally improve accuracy.

Development and validation of a reverse phase High Performance Liquid Chromatographic method, using standard addition calibration, for determination of risperidone in human plasma

Risperidone is a drug of choice in the management of psychosis and high performance liquid chromatography (HPLC) is regarded as the most sensitive and accurate method for quantitative analysis of risperidone, as well as other drugs having low plasma concentrations in biological fluids. A simple and accurate HPLC method was developed for the determination of risperidone in human plasma using the standard addition calibration technique to augment the weak signals due to low plasma concentrations of risperidone. Risperidone was eluted using isocratic mode with a mobile phase of methanol: acetonitrile (60:40) on a Chemisil ODS C18 column (250 mm×4.6 mm i.d., 5 μ particle size). The sample injection volume, flow rate, column temperature and wavelength of detection were set at 10 µl, 1.0 ml/min, 35 ˚C and 280 nm respectively. The run time for the method was 7 minutes, with risperidone having a retention time of 3.566 minutes. The method was linear within the concentration 10-50 ng/ml (R2= 0.998), with LOD and LOQ of 0.13 and 0.40 ng/ml respectively. The precision and relative error was 3.44 % and 3.38 % respectively. The developed method can be employed in the quantitative determination of risperidone in pharmacokinetic and bioequivalence studies.

Determination of Manganese in Serum Using GFAAS: Serum Reference Values for Manganese in the Adolescent Girls of the DERVAN Cohort.

Current proposed method allows for the determination of manganese in serum sample using aqueous standard calibration technique on Graphite Furnace atomic absorption spectrophotometer (GFAAS) using deuterium background correction. This method involves determination of manganese from digested serum samples without the use of matrix modifier. Pyrolysis and atomization temperatures are 1200°C and 2200°C respectively. The limit of detection (LoD) and limit of quantitation (LoQ) of the method are 0.0097ng/ml (0.18nmol/l) and 0.032ng/ml (0.58nmol/l) respectively. Validation of the method was carried out using seronorm trace element level-1 serum standard with excellent agreement between measured value and certified value. Accuracy was demonstrated by the spike and recovery study with analytical recovery between 98.8 and 100.6% in serum. The serum reference value for manganese in adolescent girls of rural Konkan region of India range from 4.7 to 215nmol/l.

Spatial Response Identification Enables Robust Experimental Ultrasound Computed Tomography.

Ultrasound computed tomography techniques have the potential to provide clinicians with 3-D, quantitative and high-resolution information of both soft and hard tissues such as the breast or the adult human brain. Their practical application requires accurate modeling of the acquisition setup: the spatial location, orientation, and impulse response (IR) of each ultrasound transducer. However, the existing calibration methods fail to accurately characterize these transducers unless their size can be considered negligible when compared with the dominant wavelength, which reduces signal-to-noise ratios below usable levels in the presence of high-contrast tissues such as the skull. In this article, we introduce a methodology that can simultaneously estimate the location, orientation, and IR of the ultrasound transducers in a single calibration. We do this by extending spatial response identification (SRI), an algorithm that we have recently proposed to estimate transducer IRs. Our proposed methodology replaces the transducers in the acquisition device with a surrogate model whose effective response matches the experimental data by fitting a numerical model of wave propagation. This results in a flexible and robust calibration procedure that can accurately predict the behavior of the ultrasound acquisition device without ever having to know where the real transducers are or their individual IR. Experimental results using a ring acquisition system show that SRI produces calibrations of significantly higher quality than standard methodologies across all transducers, both in transmission and in reception. Experimental full-waveform inversion (FWI) reconstructions of a tissue-mimicking phantom demonstrate that SRI generates more accurate reconstructions than those produced with standard calibration techniques.

Directionally Decomposing Structured Light for Projector Calibration.

Intrinsic projector calibration is essential in projection mapping (PM) applications, especially in dynamic PM. However, due to the shallow depth-of-field (DOF) of a projector, more work is needed to ensure accurate calibration. We aim to estimate the intrinsic parameters of a projector while avoiding the limitation of shallow DOF. As the core of our technique, we present a practical calibration device that requires a minimal working volume directly in front of the projector lens regardless of the projector's focusing distance and aperture size. The device consists of a flat-bed scanner and pinhole-array masks. For calibration, a projector projects a series of structured light patterns in the device. The pinholes directionally decompose the structured light, and only the projected rays that pass through the pinholes hit the scanner plane. For each pinhole, we extract a ray passing through the optical center of the projector. Consequently, we regard the projector as a pinhole projector that projects the extracted rays only, and we calibrate the projector by applying the standard camera calibration technique, which assumes a pinhole camera model. Using a proof-of-concept prototype, we demonstrate that our technique can calibrate projectors with different focusing distances and aperture sizes at the same accuracy as a conventional method. Finally, we confirm that our technique can provide intrinsic parameters accurate enough for a dynamic PM application, even when a projector is placed too far from a projection target for a conventional method to calibrate the projector using a fiducial object of reasonable size.

ICESat‐2 Atmospheric Channel Description, Data Processing and First Results

AbstractThe Advanced Topographic Laser Altimeter System (ATLAS) was launched aboard the Ice Cloud and land‐Elevation Satellite‐2 (ICESat‐2) satellite in September 2018. ATLAS is a single wavelength (532 nm) lidar system designed to acquire high resolution measurements of the earth's surface while also obtaining atmospheric backscatter from molecules, clouds, and aerosols. Because ATLAS is optimized for altimetry, the atmospheric data acquired is unique in many respects and requires non‐standard analysis techniques. For example, the high repetition rate laser limits the vertical extent of the profiles to just 14 km and causes atmospheric scattering from above 15 km to be added to the scattering in the lower 0–14 km profile. In addition, the limited vertical range of the acquired profiles renders it difficult to compute the magnitude of the solar background and hinders the application of standard calibration techniques. Despite these limitations, methods have been developed to successfully produce data products that have value to the atmospheric community for cloud and aerosol research and are currently available at the National Snow and Ice Data Center (NSIDC). In this paper we describe the ICESat‐2 atmospheric channel and the methods used to process the ATLAS raw photon count data to obtain calibrated backscatter and higher level products such as layer heights and type, blowing snow, column optical depth and apparent surface reflectance.

Autonomous in situ calibration of ion‐sensitive field effect transistor pH sensors

AbstractIon‐sensitive field effect transistor‐based pH sensors have been shown to perform well in high frequency and long‐term ocean sampling regimes. The Honeywell Durafet is widely used due to its stability, fast response, and characterization over a large range of oceanic conditions. However, potentiometric pH monitoring is inherently complicated by the fact that the sensors require careful calibration. Offsets in calibration coefficients have been observed when comparing laboratory to field‐based calibrations and prior work has led to the recommendation that an in situ calibration be performed based on comparison to discrete samples. Here, we describe our work toward a self‐calibration apparatus integrated into a SeapHOx pH, dissolved oxygen, and CTD sensor package. This Self‐Calibrating SeapHOx is capable of autonomously recording calibration values from a high quality, traceable, primary reference standard: equimolar tris buffer. The Self‐Calibrating SeapHOx's functionality was demonstrated in a 6‐d test in a seawater tank at Scripps Institution of Oceanography (La Jolla, California, U.S.A.) and was successfully deployed for 2 weeks on a shallow, coral reef flat (Lizard Island, Australia). During the latter deployment, the tris‐based self‐calibration using 15 on‐board samples exhibited superior reproducibility to the standard spectrophotometric pH‐based calibration using > 100 discrete samples. Standard deviations of calibration pH using tris ranged from 0.002 to 0.005 whereas they ranged from 0.006 to 0.009 for the standard spectrophotometric pH‐based method; the two independent calibration methods resulted in a mean pH difference of 0.008. We anticipate that the Self‐Calibrating SeapHOx will be capable of autonomously providing climate quality pH data, directly linked to a primary seawater pH standard, and with improvements over standard calibration techniques.

Scalar Dielectric Constant Extraction of Planar Materials from Reflection Measurements

Industrial plastics are widely used in warfare electromechanical systems to protect the internal electronic circuitry from environmental effects. Depending the purpose of the warfare system, the surface interaction with electromagnetic fields play a key role and the main parameter that determines reflection and the shielding of the electromagnetic fields from material surface is the dielectric constant of the material itself. In this paper, extraction of scalar dielectric constant from electromagnetic reflection measurement using an alternative two standard calibration technique in a low cost aluminum compact chamber is obtained. Calibration technique uses time domain measurements and converts them to frequency domain. Especially in R&D phase of electromechanical integration of warfare systems, this technique is quite useful where the exact values of dielectric constants of planar industrial plastics are not required. Obtained reflection coefficient error level is 0.67dB for 10mm while it reaches 1.62dB for 40mm thickness materials. It is shown that calculated values are in good agreement with the reference measurement method performed by precision airline setup Agilent 85050C.

A newly modified QuEChERS method for the analysis of organochlorine and organophosphate pesticide residues in fruits and vegetables.

A newly modified QuEChERS method was developed, validated, and tested in-house for the multiclass, multiresidue determination of organophosphate (OPP) and organochlorine pesticide (OCP) residues in fruits and vegetables. The method incorporated a solvent extraction with acetonitrile followed by partitioning with magnesium sulphate (MgSO4) and sodium chloride (NaCl). The final step involved a dispersive solid phase extraction (d-SPE) clean-up prior to gas chromatography with electron capture detection (GC-ECD) analysis. Apples and lettuce were the selected matrices for fruits and vegetables, respectively in the method development stages. Various combinations of sorbents were tested in the clean-up step. Florisil and MgSO4 (FM) d-SPE proved to be the best combination for the clean-up step for both OCPs and OPPs in both the fruit and vegetable matrices. Recovery values fell within the acceptable range of 70 to 120% (RSD ≤20%). The new method is unique as it employs the standard addition calibration technique for the quantification of OCP and OPP residues. Limit of detection, limit of quantification, linearity, recovery analysis, and repeatability were validation parameters used to evaluate the accuracy, precision, and ruggedness of the method. The newly modified QuEChERS method provides a cheaper alternative for the analysis of pesticide residues in fruits and vegetables as samples can be analysed at a fraction of the cost of the original QuEChERS method. The efficacy of the method was tested on several fruits and vegetables from the Central Division of Trinidad and Tobago. OCP and OPP residues were found in 61% of the samples, most of which were above the maximum residue limits.

Off-Line Camera-Based Calibration for Optical See-Through Head-Mounted Displays

In recent years, the entry into the market of self contained optical see-through headsets with integrated multi-sensor capabilities has led the way to innovative and technology driven augmented reality applications and has encouraged the adoption of these devices also across highly challenging medical and industrial settings. Despite this, the display calibration process of consumer level systems is still sub-optimal, particularly for those applications that require high accuracy in the spatial alignment between computer generated elements and a real-world scene. State-of-the-art manual and automated calibration procedures designed to estimate all the projection parameters are too complex for real application cases outside laboratory environments. This paper describes an off-line fast calibration procedure that only requires a camera to observe a planar pattern displayed on the see-through display. The camera that replaces the user’s eye must be placed within the eye-motion-box of the see-through display. The method exploits standard camera calibration and computer vision techniques to estimate the projection parameters of the display model for a generic position of the camera. At execution time, the projection parameters can then be refined through a planar homography that encapsulates the shift and scaling effect associated with the estimated relative translation from the old camera position to the current user’s eye position. Compared to classical SPAAM techniques that still rely on the human element and to other camera based calibration procedures, the proposed technique is flexible and easy to replicate in both laboratory environments and real-world settings.

Resurrected from the dead: Full characterization of an old HPGe detector using γ-ray and CT tomographies coupled to standard calibration techniques and simulations

A decommissioned co-axial HPGe detector has been recently acquired and returned to operational mode in an effort to build an environmental radiation spectrometer at the University of Athens. The new counting station, GEROS (Germanium for Environmental RadiOactivity Studies), was fully characterized prior to operation to obtain detailed information on its linear response, efficiency and energy resolution. In addition to using point-like calibration sources (60Co,137Cs,152Eu and 226Ra), several bulk sample geometries were calibrated by means of an IAEA standard, focusing on soils, sediments and solid materials. In lieu of deteailed technical specifications, the crystal integrity, especially in regards to the dead layer known to build up over the years was studied by means of γ-ray tomography. The 3D geometry of the crystal was fully reconstructed considering the absorption coefficients, and the dead layer thickness was estimated. The overall crystal alignment inside the case was also checked. The results were verified by placing GEROS inside a medical CT scanner and irradiating it to obtain detailed longitudinal and transverse sections. The results were combined to provide input data for subsequent MCNP5 simulations. Good overall agreement between simulations and measurements was achieved. Despite some expected loss of resolution, the detector was found to perform substantially well.

Acoustic field characterization of a clinical magnetic resonance-guided high-intensity focused ultrasound system inside the magnet bore.

With the expanding clinical application of magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU), acoustic field characterization of MR-HIFU systems is needed for facilitating regulatory approval and ensuring consistent and safe power output of HIFU transducers. However, the established acoustic field measurement techniques typically use equipment that cannot be used in a magnetic resonance imaging (MRI) suite, thus posing a challenge to the development and execution of HIFU acoustic field characterization techniques. In this study, we developed and characterized a technique for HIFU acoustic field calibration within the MRI magnet bore, and validated the technique with standard hydrophone measurements outside of the MRI suite. A clinical Philips MR-HIFU system (Sonalleve V2, Philips, Vantaa, Finland) was used to assess the proposed technique. A fiber-optic hydrophone with a long fiber was inserted through a 24-gauge angiocatheter and fixed inside a water tank that was placed on the HIFU patient table above the acoustic window. The long fiber allowed the hydrophone control unit to be placed outside of the magnet room. The location of the fiber tip was traced on MR images, and the HIFU focal point was positioned at the fiber tip using the MR-HIFU therapy planning software. To perform acoustic field mapping inside the magnet, the HIFU focus was positioned relative to the fiber tip using an MRI-compatible 5-axis robotic transducer positioning system embedded in the HIFU patient table. To perform validation measurements of the acoustic fields, the HIFU table was moved out of the MRI suite, and a standard laboratory hydrophone measurement setup was used to perform acoustic field measurements outside the magnetic field. The pressure field scans along and across the acoustic beam path obtained inside the MRI bore were in good agreement with those obtained outside of the MRI suite. At the HIFU focus with varying nominal acoustic powers of 10-500W, the peak positive pressure and peak negative pressure measured inside the magnet bore were 3.87-68.67MPa and 3.56-12.06MPa, respectively, while outside the MRI suite the corresponding pressures were 3.27-67.32MPa and 3.06-12.39MPa, respectively. There was no statistically significant difference (P>0.05) between measurements inside the magnet bore and outside the MRI suite for the p+ and p- at any acoustic power level. The spatial-peak pulse-average intensities (ISPPA ) for these powers were 312-17816W/cm2 and 220-15698W/cm2 for measurements inside and outside the magnet room, respectively. In addition, when the scanning step size of the HIFU focus was increased from 100μmto 500μm, the execution time for scanning a 4×4mm2 area decreased from 210min to 10min, the peak positive pressure decreased by 14%, the peak negative pressure decreased by 5%, and the lateral full width at half maximum dimension of pressure profiles increased from 1.15mm to 1.55mm. The proposed hydrophone measurement technique offers a convenient and reliable method for characterizing the acoustic fields of clinical MR-HIFU systems inside the magnet bore. The technique was validated for use by measurements outside the MRI suite using a standard hydrophone calibration technique. This technique can be a useful tool in MR-HIFU quality assurance and acoustic field assessment.

Novel gas chromatographic headspace techniques for measuring Single-component liquid isotherms

Abstract In this study, a novel headspace technique, based on liquid calibration, was developed and compared to the standard headspace or vapor calibration technique. The technique was applied for the measurements of single component liquid adsorption isotherms of xylene isomers, ethylbenzene and toluene on a commercial NaX (13X) zeolite. In comparison to the vapor calibration technique, the liquid calibration technique provided more effective means by faster generating liquid isotherms with more accuracy and less computational complexity. The isotherms were measured at 30, 60 and 90 °C using both headspace techniques, and the results were found reasonably consistent. Among the alkylaromatic compounds studied, the NaX zeolite was more selective to toluene and showed the lowest selectivity to m-xylene. In contrast to larger adsorption capacity of toluene compared to ethylbenzene and p-xylene, the isosteric heats of adsorption indicated that ethylbenzene and p-xylene created stronger bonds to the NaX sites. The effects of solute concentration in the liquid phase were investigated with regard to the adsorption capacity and selectivity. The results indicates that the adsorbent selectivity is generally dependent on the concentration of the solute in the solution.

Calibrating wave resource assessments through application of the triple collocation technique

Numerical wave models are often used to hindcast wave conditions and predict the theoretical energy production from wave energy conversion (WEC) devices. It is widely acknowledged that numerical model suffer from bias's and uncertainties which ultimately affect the final predictions of WEC power. In this case study, a Simulating WAves Nearshore (SWAN) hindcast, based on the ECMWF wave and FNMOC wind boundary conditions, is used to predict sea states off the Canadian west coast and the triple collocation technique is applied to quantify the model result bias's, and systematic and random errors. To analyze the error and calibrate the results from the hindcast, two in-situ collocated wave measurement devices are deployed; A TriAxys wave measurement buoy and a Nortek AWAC. The triple collocation technique is used to compare the significant wave height and energy period parameters over a three-month period, from October to December 2014. The triple collocation technique assumes linear relationship between the measured value and true value, and outputs the bias, calibration slope and the measurement random error. This study implements two previously utilized calibration regimes, a single value and monthly calibration regime, as well as presenting two novel methods to improve the impact of the calibration; a bivariate calibration and a spectral calibration. The two standard calibration techniques resulted in negligible improvements in data correlation. The spectral method suffered from high computational cost and only 3.4% improvement in significant wave height correlation. The bivariate calibration regime, following the International Electrotechnical Commission (IEC) wave resource histogram parameters, resulted in 5% and 26% improvements in the significant wave height and energy period correlations respectively. Calibration of the SWAN hindcast reduced the gross wave energy transport values by 900 MWh, yet the final WEC production estimates only varied by 1.5 MWh but greatly improved their time-series correlation. It is shown that the triple collocation technique, under the bivariate distribution regime, provides a more realistic presentation of future WEC power production and eliminates known short-comings of numerical model outputs.

Analytical evaluation of a quadruple-mode micro-flow ultrasonic nebulizer for sample introduction in microwave induced plasma spectrometry

The analytical potential of a coupled continuous-micro-flow ultrasonic nebulizer quadruple-mode micro-capillary system (μ-USN-QCS)-argon-helium microwave induced plasma-optical emission spectrometry (MIP-OES) has been evaluated for the purpose of determination of inorganic elements (Ba, Ca, Cd, Cu, Fe, Mg, Mn, Pb, Sr, Zn). The nebulizer incorporates four solution capillaries with independent liquid feeding and a common gas inlet. Four different spray chambers were evaluated and the geometry of the best performing one was optimized. A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by a determination of the limits of detection (LODs) and precision (RSDs) with the μ-USN-QCS-MIP-OES observed at a 40μLmin−1 flow rate. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were in the range from 2.8ngmL−1 for Cu to 30ngmL−1 for Ba. The method offers relatively good precision (RSD ranged from 6% to 8%) for micro-sampling analysis. The methodology was validated through determination of elements in certified reference materials (NRCC DOLT-2, NRC GBW 07302, NIST 2710 and NIST 1643e) and by the aqueous standard calibration technique. The measured of contents of elements in the reference materials were in satisfactory agreement with the certified values.

Simultaneous use of Cs and Rb Rydberg atoms for dipole moment assessment and RF electric field measurements via electromagnetically induced transparency

We demonstrate simultaneous electromagnetically-induced transparency (EIT) with cesium (Cs) and rubidium (Rb) Rydberg atoms in the same vapor cell with coincident (overlapping) optical fields. Each atomic system can detect radio frequency (RF) electric (E) field strengths through the modification of the EIT signal (Autler-Townes (AT) splitting), which leads to a direct International System of Unit traceable RF E-field measurement. We show that these two systems can detect the same RF E-field strength simultaneously, which provides a direct in situ comparison of Rb and Cs RF measurements in Rydberg atoms. In effect, this allows us to perform two measurements of the same E-field strength, providing a relative comparison of the dipole moments of the two atomic species. This gives two measurements that help rule out systematic effects and uncertainties in this E-field metrology approach, which are important when establishing an international measurement standard for an E-field strength, and is a necessary step for this method to be accepted as a standard calibration technique. We use this approach to measure E-fields at 9.2 GHz, 11.6 GHz, and 13.4 GHz, which correspond to three different atomic states (different principal atomic numbers and angular momentums) for the two atom species.

Determination of Arsenic in Sinus Wash and Tap Water by Inductively Coupled Plasma–Mass Spectrometry

Arsenic is a toxic element to which humans are primarily exposed through food and water; it occurs as a result of human activities and naturally from the earth’s crust. An experiment was developed for a senior level analytical laboratory utilizing an Inductively Coupled Plasma–Mass Spectrometer (ICP–MS) for the analysis of arsenic in household sinus wash and tap water. This powerful instrumental technique can be used to elucidate the elemental composition of a complex sample while offering the benefits of high-precision quantitative analysis. The chosen matrices further provided the opportunity to demonstrate two important analytical concepts. First, the sinus wash samples displayed signal suppression, illustrating the necessity for employment of the internal standard calibration technique. Second, the high chloride matrix of the sinus wash led to the formation of the ArCl+ polyatomic ion in the argon plasma, which overlapped with arsenic’s single isotope at m/z = 75. Analysis was performed in no gas mode...