Calibration Validation Research Articles

Validation of the ATLAS hadronic calibration with the LAr End-Cap beam tests data

The high granularity of the ATLAS calorimeter and the large number of expected particles per event require a clustering algorithm that is able to suppress noise and pile-up efficiently. Therefore the cluster reconstruction is the essential first step in the hadronic calibration. The identification of electromagnetic components within a hadronic cluster using cluster shape variables is the next step in the hadronic calibration procedure. Finally the energy density of individual cells is used to assign the proper weight to correct for the invisible energy deposits of hadrons due to the non-compensating nature of the ATLAS calorimeter and to correct for energy losses in material non instrumented with read-out.The weighting scheme employs the energy density in individual cells. Therefore the validation of the monte carlo simulation, which is used to define the weighting parameters and energy correction algorithms, is an essential step in the hadronic calibration procedure.Pion data, obtained in a beam test corresponding to the pseudorapidity region 2.5 < |η| < 4.0 in ATLAS and in the energy range 40 GeV ≤ E ≤ 200 GeV, have been compared with monte carlo simulations, using the full ATLAS hadronic calibration procedure.

Comparison of two commercial detector arrays for IMRT quality assurance

Two commercially available detector arrays were compared for their use in the quality assurance of patient‐specific IMRT treatment plans: one a diode‐based array (MapCHECK) and the other an ion chamber‐based array (MatriXX). The dependence of the response of detectors on field size, dose rate, and radiation energy was measured and compared with reference measurements using a Farmer‐type ionization chamber. The linearity of the detector response, short‐term and long‐term reproducibility, statistical uncertainty as a function of delivered dose, and the validity of the array calibration were also examined to understand the stability and uncertainty of the systems. No field size or SSD dependence was observed within the range of the field sizes and SSDs used in the study at both 6 MV and 18 MV photon energies. Both detector arrays showed negligible errors (<1%) when measuring doses of more than ~8 cGy, but exhibited errors of ~3% when measuring doses on the order of 1 cGy. While the MapCHECK showed a stable short‐term reproducibility to within measurement error, the MatriXX showed a slow but continuous increase in readings during the initial one‐hour period (about 0.8%). The MapCHECK also showed a slightly better array sensitivity correction with all the detectors having less than 1% discrepancy and more than 90% of the detectors within 0.5% variation, whereas about 60% of the MatriXX detectors showed a less than 0.5% variation and ~8% exhibited a larger than 1% discrepancy. MatriXX detectors also displayed a volume‐averaging effect consistent with its detector size of ~4.5 mm in diameter. Excellent passing rates were obtained for both detector arrays when compared with the planar dose distributions from the treatment planning system for three 6 MV IMRT fields and three 18 MV IMRT fields after the volume‐averaging effect of the MatriXX was taken into account.PACS number: 87.55.km; 87.55.Qr; 87.56.Fc

Rapid Estimation of Aedes aegypti Population Size Using Simulation Modeling, with a Novel Approach to Calibration and Field Validation

Rapid Estimation of Aedes aegypti Population Size Using Simulation Modeling, with a Novel Approach to Calibration and Field Validation

Use of near-infrared reflectance spectroscopy to predict the percentage of dead versus living grass roots

We tested the potential of near-infrared reflectance spectroscopy (NIRS) to predict the percentage of dead versus living roots of five grass species grown in monocultures under field conditions. Root death was induced after total severance of aboveground vegetation. Root samples were collected immediately after this treatment to obtain predominantly live roots (L), and then one (D1) and two months (D2) to obtain dead roots. NIRS spectra of L samples were different from D1 and D2 samples for four of the five species. The percentage of live and dead roots and root C and N were significantly predicted by NIRS. Validation of live and dead root percentage calibration was achieved with an error of prediction of 15%. These results show the potential of NIRS to predict the percentage of dead and live roots under field conditions and open up new opportunities in estimating more accurately below-ground net primary production of grasslands.

Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration

Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.

Number‐average molecular weight of branched polymers from SEC with viscosity detection and universal calibration

AbstractBACKGROUND: Number‐average molecular weight, M̄n, is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size‐exclusion chromatography (SEC) using on‐line viscometric detection and assuming the validity of the universal calibration concept.RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on‐line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M̄n and weight‐average molecular weight, M̄w. Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules.CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η]M, on elution volume, can differ in values of [η]M from those obtained for narrow molecular weight standards by 10–15%. The method studied is helpful for the determination of M̄n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers. Copyright © 2008 Society of Chemical Industry

Validation of primary hydrophone calibrations by inter‐laboratory comparisons and by independent calibration methods

A description is presented of two approaches which may be used to validate primary calibration methods for hydrophones and transducers. Firstly, a comparison may be made with another independent absolute calibration method, preferably one based on a different physical principle (and therefore with few common sources of uncertainty). Secondly, an inter‐laboratory comparison of calibrations may be undertaken between different institutes operating at a similar level. This paper describes the results of such exercises for free‐field calibration of hydrophones in the range from 1 kHz to 500 kHz. Firstly, two independent calibration methods are compared: the three‐transducer reciprocity method and a method based on optical interferometry. The differences observed in the results are typically less than 0.5 dB, which is of the same order as the overall uncertainties of each of the methods. Secondly, the results are shown of a recent international comparison of hydrophone calibrations involving institutes from Canada, China, Germany, Russia, South Africa, UK, and USA. Here, the agreement was generally within quoted uncertainties, the results generally lying within a ±0.5 dB band for frequencies up to 300 kHz. A discussion is given of the general sources of uncertainties in the calibrations.

Calibration and multiple data set-based validation of a land surface model in a mountainous Mediterranean study area

A detailed understanding of the magnitude of the different components of the hydrologic cycle in Mediterranean mountainous catchments is important for a number of different reasons, such as reservoir management and land use planning. Since it is currently impossible to fully monitor a catchment continuously in a spatially distributed manner, the only way to obtain estimates of the different water and energy balance terms is the application of hydrologic models. These models rely on a large number of parameters, of which estimates are rarely available. The objective of this paper is to assess to which degree the overall performance of a hydrologic model can be improved through the estimation of model parameters using observed soil moisture values. In situ observations of soil moisture, surface runoff, infiltration, and soil temperature in the Ribera Salada catchment in the Southeastern Pyrenees are used for this purpose. Before calibration, the model yielded poor results for all these variables. The use of soil and TOPMODEL parameters estimated using one year of soil moisture observations improved the modeled soil moisture values throughout the study period. A strong improvement in the modeled surface runoff and infiltration was also obtained. The model has been found to adequately reproduce the observed soil temperature. As a summary, the results indicate that using one year of soil moisture observations to calibrate a hydrologic model in Mediterranean mountainous catchments may be sufficient, and that this parameter estimation can lead to a strong improvement in the overall model performance.

Relating changes in duff moisture to the Canadian Forest Fire Weather Index System in Populus tremuloides stands in Elk Island National Park

The manner in which trembling aspen ( Populus tremuloides Michx.) forest duff moisture changes during the growing season was investigated in Elk Island National Park, Alberta, Canada. A calibration–validation procedure incorporating one calibration site with moisture sampling across three topographic positions was used to develop predictive models, which were subsequently compared with 12 validation sites across three vegetation types throughout the Park. Duff moisture was modelled against the Duff Moisture Code and Drought Code components of the Canadian Forest Fire Weather Index System. Spring, summer, and fall rates of duff moisture change differed (P &lt; 0.050) during calibration, with moisture loss greatest in spring. Additionally, while moisture changes on the south-facing and crest topographic positions were similar during spring, moisture losses were greater (P &lt; 0.050) at these locations compared with the north-facing landscape position. Correlation analysis indicated that duff inorganic content and bulk density were both related to duff moisture but were limited in importance compared with weather-based influences. When compared with predicted values obtained from calibrated models, moderate predictability of duff moisture was found (mean absolute error = 20.7%–54.2%). Relative to the national standard equations, unique but very different empirical relationships were developed between the Duff Moisture Code and Drought Code and the moisture content of the duff layer in aspen forest stands found in Elk Island National Park.

Comparing Performance and Parameterization of a One‐Dimensional Unsaturated Zone Model across Scales

The utility of an unsaturated zone soil moisture model is not only its ability to describe the soil moisture dynamics at a given point but also the possibility to generalize the results to larger areas. In this study we investigated the predictive performance of a one‐dimensional unsaturated zone soil moisture model when applied at point, field, response unit, and catchment scales, using detailed field observations from a 0.42‐km2 catchment in the Netherlands. Our main question was how model parameterization and model performance could be compared across these scales. We considered two different calibration–validation schemes and three performance statistics. In all cases we applied the same Levenberg–Marquardt optimization scheme. Differences between calibration–validation schemes (interpolation vs. extrapolation) were surprisingly small. Using one particular model parameterization across the various aggregation levels, the optimal Mualem–van Genuchten parameters for a coarser aggregation level can be derived from an underlying level by simple arithmetic averaging. The different performance indices (RMSE, index of agreement, and Nash–Sutcliffe coefficient) were highly variable between observation locations and for different aggregation levels. Overall, the indices were more favorable at higher aggregation levels, and in correspondence with errors reported in comparable studies. The unsaturated‐zone model did not, however, provide satisfactory predictions of independent flux observations, in this case daily catchment discharge. Moreover we did not succeed in deriving a meta‐model to scale model performance indices with aggregation level. Our case study therefore supports the view that multiscale calibration studies that use both state and flux observations are required to compare results from unsaturated zone models at different aggregation levels.

Screening of Wheat for Flour Swelling Volume by Near‐Infrared Spectroscopy

ABSTRACTSelection for starch quality is an important consideration in the breeding of wheat for Asian noodles, particularly Japanese udon, and the flour swelling volume (FSV) test was developed for this purpose. Near‐infrared reflectance spectroscopy (NIRS) analysis has also been a key tool in recent years in wheat quality selection. The development and validation of NIRS calibrations for the prediction of FSV on whole grain involved 22 cultivars and breeding lines grown at four locations in two seasons. Eight calibrations were developed, each based on samples from seven trials, with the eighth trial used for validation. Over the eight calibrations, r2 between predicted and actual values was 0.56–0.86 (mean 0.74) and the standard error of prediction (SEP) was 0.77–1.65 (mean 1.14) mL/g of dry meal. Separate calibrations were also developed for hard (n = 461), soft (n = 150), and soft+hard grain (n = 616), with standard errors of cross‐validation (SECV) of 1.03, 1.39, and 1.21 mL/g of dry meal, respectively. Corresponding r2 between predicted and actual values were 0.76, 0.78, and 0.76, respectively. Thus, NIRS offers good potential for the screening of early‐generation lines to identify those with high or low FSV.

SU-FF-T-127: Comparison of Two Commercial Detector Arrays for IMRT Quality Assurance

Purpose: to evaluate the suitability of two commercial detector arrays for IMRT patient‐specific quality assurance.Method and Materials: The two detector arrays investigated are the MapCHECK diode array and the ImRT MatriXX ionization chamber array. We examined the linearity of the detector response, short‐term and long‐term reproducibility, statistical uncertainty as a function of delivered dose, and the validity of the array calibration. The dependence of the response of detectors on the field size, dose rate, and radiation energy were also studied. Finally, radiochromic EBT films were used to compare the results with those from the two detector arrays for three IMRT fields. Results: Both detector readings showed excellent agreement (<0.5%) with Farmer chamber measurement with varying field size and SSD in both 6 MV and 18 MV photo beams. While the MapCHECK showed a stable short‐term response (<0.3% variation), the MatriXX showed a continuously slow increase in reading during the one‐hour period (an increase of about 0.8%). Both detectors showed a fluctuation of about 1% during the one‐month period. The MapCHECK also showed a slightly better array sensitivity correction with all the detectors having less than 1% discrepancy and more than 90% of the detectors within 0.5% variation. On the other hand, about 60% of the MatriXX detectors showed a less than 0.5% variation and ∼8% exhibited a larger than 1% discrepancy. Using the commonly used 3%/3mm criteria, both detector arrays had more than 95% passing rate for the three IMRT fields when compared with the EBT film. Conclusion: The two detector arrays showed no field size, SSD, and energy dependent response with stability of better than 1% in most cases and are suitable for IMRT patient‐specific quality assurance. This work was supported in part by NCI grants R01‐CA‐100636.

A Small Autonomous Surface Vehicle for Ocean Color Remote Sensing

This paper provides a study on the development and the use of a small autonomous surface vehicle (ASV) that automatically follows programmed mission transects, while measuring sensor outputs along the tracks. It discusses the mechanical construction of the ASV, the distributed architecture of controller area network (CAN)-based nodes for science and vehicle payloads, high-speed radio-frequency (RF) communications, the performance of the heading autopilot, global positioning system (GPS)-based guidance algorithm, and the mission programming technique. The field trials of the ASV, performed off the coast of Goa, India, are focused on retrieving the 2-D spatial distribution of surface chlorophyll, which is one of the useful parameters in characterizing the nature of calibration-validation (CALVAL) sites for ocean remote sensing needs. A further benefit of ASVs is that they can be built at a low cost and used in monitoring applications of diverse coastal ecosystems.

Validation of a quality assessment system for blood gas and electrolyte testing

Background A recently-introduced quality assessment system (Intelligent Quality Management: iQM™), was evaluated in routine clinical use at four different hospitals. The iQM technology is designed to replace conventional external liquid controls with software, Process Control (PC) Solutions and Calibration Validation components that continually assess the function of the GEM ® Premier™ 3000 (GEM) analyzer and automatically initiate and document corrective actions. Methods We validated the performance claims of iQM by monitoring quality control (QC) materials at 4 clinical sites while analyzing approximately 10,550 patient samples. We compared iQM-measured QC values to traditional QC results, evaluating the number and type of error flags for patient samples, and used data from control results to calculate the average time to detect an error (ADT) for each analyte. Results The calculated ADT was approximately 3 min for all analytes except for sodium (17 min), glucose (11 min), and lactate (5.9 min). Precision of control materials in iQM cartridges was better than from external controls run on traditional analyzers. The iQM system detected errors in 0.46% of actual clinical samples. Conclusions The findings from our study confirm that (a) iQM precision in a clinical setting is comparable to that found in previous studies done in a research setting, (b) the improved precision of control material on the iQM is likely because the internal control fluids are sealed and not susceptible to exposure from handling, and (c) the system detects and often corrects errors in specific samples that might not be reported by traditional analytical systems.

Simulating badland erosion with KINEROS2 in a small Mediterranean mountain basin (Vallcebre, Eastern Pyrenees)

The Ca lʻIsard catchment (1.32 km 2), a sub-basin of the Vallcebre experimental catchments, yields large amounts of sediments (about 580 Mg km − 2 year − 1 ) that are produced in relatively small but very active eroded areas (badlands). Several lines of evidence suggest that there is a delay between sediment production, caused by intense summer rainstorms, and sediment transport, occasioned by the main floods produced by large precipitation events following wet antecedent conditions. First, a calibration–validation exercise was carried out with sediment yield data obtained using containers provided with slot divisors in a badlands micro-catchment (1240 m 2). Then, the model was applied to the main badlands areas in the Ca lʻIsard sub-catchment for a 4-year period and the simulated sediment yields were compared with the records at the gauging station. The test was performed with the Generalized Likelihood Uncertainty Estimation (GLUE) approach for assessing the uncertainty associated with model predictions, which assumes that many parameter sets can give acceptable simulations. The results demonstrated the capacity of KINEROS2 to simulate badland erosion, although it showed limited robustness. A clear temporal mismatch between erosion and sediment transport and the relevance of sediment stores in the catchment were confirmed, while the total weights of sediment were generally under-predicted. The limited suitability of the area used for calibration or the role of sediment sources not simulated in the approach may account for this shortcoming.

Measurements of the Total Water Content of Cirrus Clouds. Part I: Instrument Details and Calibration

Abstract This paper describes an instrument designed to measure the sum of gas phase and solid phase water, or total water, in cirrus clouds, and to be mounted in a pallet in the underbelly of the NASA WB-57 research aircraft. The ice water content of cirrus is determined by subtracting water vapor measured simultaneously by the Harvard water vapor instrument on the aircraft. The total water instrument uses an isokinetic inlet to maintain ambient particle concentrations as air enters the instrument duct, a 600-W heater mounted directly in the flow to evaporate the ice particles, and a Lyman-α photofragment fluorescence technique for detection of the total water content of the ambient air. Isokinetic flow is achieved with an actively controlled roots pump by referencing aircraft pressure, temperature, and true airspeed, together with instrument flow velocity, temperature, and pressure. Laboratory calibrations that utilize a water vapor addition system that adds air with a specific humidity tied to the vapor pressure of water at room temperature and crosschecked by axial and radial absorption of Lyman-α radiation at the detection axis are described in detail. The design provides for in-flight validation of the laboratory calibration by intercomparison with total water measured by radial absorption at the detection axis. Additionally, intercomparisons in clear air with the Harvard water vapor instrument are carried out. Based on performance of the Harvard water vapor instrument, this instrument has the detection capability of making accurate measurements of total water with mixing ratios in the mid- to upper troposphere of up to 2500 ppmv and mixing ratios in the lower stratosphere of about 5 ppmv, corresponding to almost three orders of magnitude in measurement capability.

Multivariate optimization of the factors influencing the solid-phase microextraction of pyrethroid pesticides in water

A method based on solid-phase microextraction (SPME) and gas chromatography with micro-electron capture detection (GC-μECD) has been optimized for the analysis of pyrethroids in water samples. The influence of parameters such as temperature, fibre coating, salting-out effect and sampling mode on the extraction efficiency has been studied by means of a mix-level factorial design, which allowed the study of main effects as well as two factor interactions. Finally, a method based on direct SPME at 50 °C, using polydimethylsiloxane fibre is proposed. The method showed good linearity ( R 2 > 0.995) and repeatability (RSD ≤ 16%) for all compounds, with detection limits ranging from 0.05 pg/mL for transfluthrin to 2.18 pg/mL for permethrin, and in general ≤1 pg/mL for most pyrethroids. Reliability was demonstrated through the evaluation of the recoveries in different water samples, such as tap water, groundwater, river water, runoff water, and wastewater. These studies demonstrated the validity of external standard calibration to quantify the target compounds in real samples, including a simple dilution step for the most complex matrices, which notoriously simplifies quantification by SPME.

Predicting Extractives, Lignin, and Cellulose Contents Using Near Infrared Spectroscopy on Solid Wood in Eucalyptus globulus

Near infrared reflectance (NIR) spectroscopy can be used to reliably predict both the physical and chemical wood properties of Eucalyptus. However, studies have been based on ground wood, which is costly and time‐consuming to obtain. Predicting wood traits from NIR spectral data taken from solid wood would greatly increase the speed and cost‐effectiveness of this procedure. Existing ground wood calibrations were evaluated for the prediction of wood chemistry from NIR spectral data taken from solid wood. Extractives, acid‐soluble lignin, and Klason lignin contents were poorly predicted. Total lignin and cellulose contents showed moderate relationships between laboratory values and the NIR predicted values. NIR calibrations were further developed specifically for predicting wood chemistry from solid wood. All calibrations had high R2 values from 0.72 to 0.88, and standard errors of calibration were less than 1.37%. Calibration validation produced high correlation coefficients between predicted and laboratory values for extractives, Klason lignin, total lignin, and cellulose contents with R2 values ranging from 0.67 to 0.87. Acid‐soluble lignin content was poorly predicted. This study showed that NIR analysis on solid wood of E. globulus could be reliably used to predict extractives, lignin, and cellulose contents. It also determined that existing ground wood calibrations, although they could give crude estimates of the wood chemistry values, would need to be re‐developed for accurate predictions from solid wood.

A potentially significant on-wafer high-frequency measurement calibration error

High accuracy radio-frequency (RF) measurements typically require a calibration to remove the undesired effects of the measurement apparatus. The calibration consists of measuring some combination of known standards such as short, open, load, through, and delay. When measurements are performed on-wafer for silicon RF integrated circuits (RFICs), a two-step calibration/de-embedding technique is typically used. First, the measurement system is calibrated to a reference plane located at the probe tips through measurement of calibration standards fabricated on an impedance-standard substrate. Second, on-wafer de-embedding standards are measured in an attempt to shift the reference plane to the terminals of the device under test (DUT). While significant effort has gone into the development of improved on-wafer de-embedding schemes, discrepancies between actual and de-embedded data still exist. In this article, we first discuss a specific case (a spiral inductor on silicon) for which there was a significant discrepancy between measurement and analysis. The problem is found to be with the measurement. This problem is detailed, and a technique we call "synthetic calibration" is described that can be used with any electromagnetic (EM) analysis to quantify calibration error for any proposed set of calibration standards. Due to the high expense and time required for wafer fabrication, it is important to successfully complete such a calibration validation prior to tape-out.

ESTIMATING DENSITY AND PULPING YIELD OF E. globulus WOOD: COMPARISON OF NEAR-INFRARED (NIR) AND MID-INFRARED (MIR)

The application of near-infrared (NIR) spectroscopy as a tool for the rapid determination of pulp yield and basic density of Eucalyptus globulus wood is described. Previously, we had examined these properties using mid-infrared (MIR) spectroscopy. More precise results were obtained based on NIR spectra where the calibrations models were more robust and better predictors than obtained for the MIR spectra. Twenty-seven samples were used for establishing the correlations (calibration) and three for making predictions based on the calibration (validation). Quant+ chemometrics software was used to obtain the calibration and prediction through principal components regression (PCR). A PCR model based on NIR spectra gave fits with a standard error of prediction (SEP) of 14.3 kg m-3 and 1.57% for basic density and pulping yield, respectively. Using PCR-MIR, the SEP values obtained were 21.44 kg m-3 and 1.73%. The method readily predicts yield (correlation coefficient: R2= 0.51), and density (correlation coefficient: R2 = 0.94) from spectral NIR measurement. Both NIR and MIR performed better in the analysis of the density property than for the pulp yield of the hardwood samples