Calibration Function Research Articles

Calibration and response function of a compact silicon-detector set-up for charged-particle spectroscopy using GEANT4

A complete methodology for detector calibration and energy-loss correction in charged-particle spectroscopy is presented. This has been applied to a compact set-up of four silicon detectors used for beta-delayed particle spectroscopy. The characterisation of the set-up was carried out using GEANT4 Monte Carlo simulations and standard alpha-calibration sources. The response function of the system was in this way accurately determined to be used for spectral unfolding.

Temporal stability of calibration functions in the traditional pure rotational Raman lidar technique

Pure rotational Raman (PRR) lidars should be calibrated to measure atmospheric temperature. In the frame of the traditional PRR technique, the lidar calibration represents the determination of calibration function (CF) coefficients using a reference temperature profile from an atmosphere model or radiosonde data. When a measurement campaign lasts several days, the accuracy of temperature retrieval from PRR lidar signals depends on the temporal stability of the selected CF. In this paper, we present a simple way to intercompare different CFs and determine the most stable function in time among them. We study to what extent the CF coefficients determined on one of the measurement campaign days may be used for temperature retrieval on the other days. We also examine the situation when reference radiosonde data are absent on one of the measurement days and, therefore, the CF coefficients need to be determined from reference data over the remaining days. The 1-week and 3-day temporal stabilities of five CFs are studied on the example of nighttime temperature profiles retrieved from PRR lidar measurements of 1, 6, 7, and 8 April 2015. The stability of these CFs is studied for the first time. The measurements were performed in Tomsk (56.48°N, 85.05°E, Western Siberia, Russia) using a PRR lidar of the Institute of Monitoring of Climatic and Ecological Systems (IMCES). The CF retrieving temperature of the troposphere (3–9 km) with the highest accuracy for the considered 1-week and 3-day measurement periods is determined for the IMCES lidar.

Evaluation of Soil Moisture Sensing Technologies in Silt Loam and Loamy Sand Soils: Assessment of Performance, Temperature Sensitivity, and Site- and Sensor-Specific Calibration Functions

<b>Highlights</b> <list list-type=bullet><list-item> Nine soil moisture sensors were evaluated in two soil types under different installation orientations. </list-item><list-item> Sensor-specific and soil-specific calibration functions were developed and validated. </list-item><list-item> Sensor performance improved substantially (31% to 89%) after calibration. </list-item><list-item> On average, sensor performance was 67% better in loamy sand than in silt loam soil. </list-item></list> <b>Abstract</b>. Reliable soil moisture information is vital for optimal irrigation management, farm-level agronomic decision-making, hydrologic studies, and cropping systems modeling. A wide range of soil moisture sensing technologies is commercially available, but their performance must be evaluated for diverse conditions of use. In this research, we investigated nine soil moisture sensors based on time-domain reflectometry, capacitance, and electrical resistance principles in production field conditions with two installation orientations, i.e., vertical (V) and horizontal (H), in two soils (silt loam and loamy sand) and two growing seasons (2017 and 2018). Performance parameters deduced from the 2017 datasets revealed that sensor type and soil type significantly affected the soil moisture sensor performance under factory calibration (F.C.); however, sensor installation orientation did not. Thus, the sensors were only evaluated based on their performance in horizontal orientation in both soils. Precision and accuracy were considered targets to assist in appropriate sensor selection. To improve sensor accuracy, site-specific calibration (S.S.C.) functions were developed and validated using independent datasets from 2018. Considering mean bias error (MBE), all sensors overestimated volumetric soil water content (θv) in both soils, with the exception of TEROS 21 (MPS-6) in silt loam and JD probe in loamy sand. On average, sensor performance was 67% better in loamy sand than in silt loam. Overall, the sensors showed higher precision in silt loam (R2 = 0.53 to 0.93) than in loamy sand (R2 = 0.25 to 0.82). Substantial post-S.S.C. improvement (32% to 89%) was observed in all sensors‘ performance relative to F.C. in silt loam. In loamy sand, while most sensors performed reasonably well with F.C., considerable improvements (28% to 85%) were observed with S.S.C. Significant differences (p < 0.05) were observed in sensors‘ sensitivity to soil temperature (Tsoil), which ranged from 14°C to 23°C in silt loam and from 14°C to 25°C loamy sand during the experiments. The CS655, 10HS, 5TE, and TEROS 21 (MPS-6) sensors showed significant (p < 0.05) sensitivity to Tsoil fluctuations, with Tsoil explaining a maximum of 17% of the variance observed in sensor performance. No statistically significant (p > 0.05) sensitivity was detected for any of the sensors in loamy sand. TEROS 21 (MPS-6) had the highest sensitivity to Tsoil with a slope of -4.25. In contrast, while statistically significant (p < 0.05), 5TE was the least sensitive to Tsoil variability with a slope of 1.81. The information, data, and analyses presented here can be instrumental for informed sensor selection and use in decision-making in production fields with similar soil textures and soil water regimes.

Free-Space Transmission Dielectric Properties Measurement Based on Six-Port Technology

A six-port technology operating in transmission mode was developed for accurate determination of dielectric properties of low-loss materials from space measurements. The transmission coefficient was obtained by using the ratio of incident waves at ports 1 and 2 of the six-port network, while the power readings were performed at ports 3-6 simultaneously. The incident wave at port 1 originated from a forward propagating electromagnetic wave passing through the material sample. The incident wave at port 2 was the reference signal related to the incident wave at port 1 before or after propagating through the material. The calibration function is developed. The proposed six-port measurement technique was demonstrated at 5.8 GHz for purpose of verification. The material sample was placed between transmitting and receiving antennas. The microwave signal from the oscillator was fed to the transmitting antenna. The receiving antenna collected the signal and sent it to port 1. Two configurations were set up at port 2, either connected to the microwave signal from the oscillator or terminated with an electrical load. Magnitude and phase measurement results for various thicknesses of dielectric slabs compared well with those obtained with a commercial automatic vector network analyzer (ANA). Similarly, dielectric properties measurements on polypropylene, acrylic, and acetal spheres also agreed well with those obtained by the ANA.

ФІЗИЧНЕ МОДЕЛЮВАННЯ ДЛЯ ВИМІРЮВАННЯ ГУСТИНИ ПРИПОВЕРХНЕВИХ ГІРСЬКИХ ПОРІД ПРИ КАРОТАЖІ НА КАБЕЛІ ТА В ПРОЦЕСІ БУРІННЯ

The results of the creation of full-scale physical models of rocks for the calibration of combined tools of radioactive logging, which include density logging, are presented. Four sets of models were built for different logging problems. 1. Models of porous carbonate reservoirs with borehole (diameter 216 mm), equipped with interchangeable simulators of casing columns (146 mm і 168 mm) with cement sheath and tubing. The models are aimed to calibrate wireline logging tools for investigating the section of uncased and cased oil&amp;gas wells. 2. Models of rocks of different density with borehole (160 mm), equipped with interchangeable drill collars (120 mm, 108 mm, 89 mm). The models are designed to calibrate density tools for logging while drilling horizontal oil&amp;gas wells. 3. Universal models of porous carbonate reservoirs, crossed by holes of three diameters (200 mm, 160 mm, 125 mm). The purpose of the models is to calibrate wireline logging tools for investigation of section of uncased and cased oil&amp;gas wells and tools for logging while drilling horizontal oil&amp;gas wells. 4. Models of near-surface rocks of different density, equipped with a steel pipe (diameter of 51 mm) closely fitting to rock. The purpose of the models is to calibrate density tools for investigation of near-surface rocks when solving engineering-geological, seismic microzoning, ecological, etc problems. Physical models were designed and constructed by the employees of the Institute of Geophysics of the National Academy of Sciences of Ukraine together with partner organizations. The regular use of the models is due to the active work carried out by the Institute of Geophysics, together with partners, to create apparatus-methodical complexes of radioactive logging, which include the density logging. Graduation relationships and calibration functions for new density logging tools, obtained on the constructed physical models, as well as examples of density determination in different well conditions when solving research-and-production problems, are given.

Application of Sensitivity Encoding Reconstruction for MRI with BOLD Signal

The work of this paper analyzes the performance of Sensitivity Encoding (SENSE) through actual data sets and determines the problem of computational efficiency. It corrects the error of the detection signal through the calibration function of the percentage signal change, and uses the three-dimensional sensor image reconstruction technology to calibrate the sensitivity of the blood to the magnetic change, enhances the sensitivity of the magnetic susceptibility gradient, and reduces the scanning time of the MRI experiment. The actual data set handles the image resolution. The performance and experimental results of SENSE are analyzed through actual data sets.

Determination of the local magnitudes of small earthquakes using a dense seismic array in the Changning−Zhaotong Shale Gas Field, Southern Sichuan Basin

With the development of unconventional shale gas in the southern Sichuan Basin, seismicity in the region has increased significantly in recent years. Though the existing sparse regional seismic stations can capture most earthquakes with <inline-formula><tex-math id="M1">\begin{document}$ {M}_{\mathrm{L}}\ge 2.5 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M1.jpg"></graphic><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M1.png"></graphic></alternatives></inline-formula>, a great number of smaller earthquakes are often omitted due to limited detection capacity. With the advent of portable seismic nodes, many dense arrays for monitoring seismicity in the unconventional oil and gas fields have been deployed, and the magnitudes of those earthquakes are key to understand the local fault reactivation and seismic potentials. However, the current national standard for determining the local magnitudes was not specifically designed for monitoring stations in close proximity, utilizing a calibration function with a minimal resolution of 5 km in the epicentral distance. That is, the current national standard tends to overestimate the local magnitudes for stations within short epicentral distances, and can result in discrepancies for dense arrays. In this study, we propose a new local magnitude formula which corrects the overestimated magnitudes for shorter distances, yielding accurate event magnitudes for small earthquakes in the Changning−Zhaotong shale gas field in the southern Sichuan Basin, monitored by dense seismic arrays in close proximity. The formula is used to determine the local magnitudes of 7,500 events monitored by a two-phased dense array with several hundred 5 Hz 3C nodes deployed from the end of February 2019 to early May 2019 in the Changning−Zhaotong shale gas field. The magnitude of completeness (<inline-formula><tex-math id="M2">\begin{document}$ {M}_{\mathrm{C}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M2.jpg"></graphic><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M2.png"></graphic></alternatives></inline-formula>) using the dense array is −0.1, compared to <inline-formula><tex-math id="M3">\begin{document}$ {M}_{\mathrm{C}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M3.jpg"></graphic><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M3.png"></graphic></alternatives></inline-formula> 1.1 by the sparser Chinese Seismic Network (CSN). In addition, using a machine learning detection and picking procedure, we successfully identify and process some 14,000 earthquakes from the continuous waveforms, a ten-fold increase over the catalog recorded by CSN for the same period, and the <inline-formula><tex-math id="M4">\begin{document}$ {M}_{\mathrm{C}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M4.jpg"></graphic><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="lijunlun-F_M4.png"></graphic></alternatives></inline-formula> is further reduced to −0.3 from −0.1 compared to the catalog obtained via manual processing using the same dense array. The proposed local magnitude formula can be adopted for calculating accurate local magnitudes of future earthquakes using dense arrays in the shale gas fields of the Sichuan Basin. This will help to better characterize the local seismic risks and potentials.

MMI–Calibration 3.0 Program

A unified program for processing the calibration protocol data of a measurement instrument under normal conditions is developed. The result of the calibration contains a calibration function (function of corrections in the form of a continuous power series) and a calibration chart based on typical probability distributions of an additive error. The problem of statistical processing of the calibration protocol data of a measurement instrument under normal conditions within the framework of the MMI–calibration 3.0 unified program is solved. An example of a calibration of a thermometer by a third-grade working standard by means of the newly developed MMI–calibration 3.0 program is presented.

Metric-Based Visual Acuity and Defocus Curve Simulation of Two Multifocal Intraocular Lens Models.

PurposeTo predict clinical defocus curve performance of the PanOptix intraocular lens (IOL) model TFNT00, a population-based image quality metric was applied to a pseudophakic eye model.MethodsVisual acuity (VA) was simulated using a 2-surface reduced eye model. For each virtual eye, the derived corneal surface was combined with scaled IOL surface. Corneal power and aberration, anterior chamber depth, and pupil size were iterated using a Monte-Carlo approach. Image quality of the IOLs was assessed using the total aberration map to compute the amplitude point spread function. A diffraction-normalized light-in-the-bucket metric was calculated for each virtual eye for defocuses from −3.5 D to +1.0 D (step size 0.25 D) and transformed to VAs and defocus curves. Simulated VA for the ReSTOR +3.0 D lens was used to generate a calibration function by linear regression correlation of simulated data with clinical VA data. Simulated TFNT00 VA was then validated by comparing defocus curves to clinical TFNT00 data.ResultsFrom −3.5 D to +1.0 D, the simulated defocus curve was generally consistent with the defocus curve from the TFNT00 clinical trial. The mean absolute difference was 0.022 logMAR (~1 letter) for simulated VA versus clinical trial VA.ConclusionIOL image quality can be assessed using a population-based virtual eye model to simulate VA and predict clinical performance. Computational modeling and simulation can be applied to future IOL development before clinical trials are conducted.

Nondestructive Sensing of Water Activity From Measurement of the Dielectric Properties at Microwave Frequencies

A rapid, nondestructive method for determining water activity of granular and particulate materials from measurement of the dielectric properties at a single microwave frequency is presented. Results are shown for almond kernels at 8 GHz and 25 °C. Situations in which bulk density is known and unknown were considered. For situations, when bulk density is known, direct correlations between the dielectric properties and water activity were identified. When the bulk density is unknown, correlations between the loss tangent (tan δ) and a density-independent calibration function (ψ), expressed in terms of the dielectric properties and water activity, were used. For purposes of illustration, analytical expressions of the water activity are derived for each situation for almond kernels for which the dielectric properties were measured at 8 GHz and 25 °C. In both situations, the dielectric constant, loss factor, loss tangent, and ψ increased exponentially with water activity. The standard error of calibration (SEC) was calculated to evaluate the effectiveness of each of these analytical expressions in predicting water activity from dielectric properties measurement. The SEC ranged from 0.02 to 0.04 for almond kernels with water activity ranging from 0.5 to 0.9 and moisture content ranging from 4.8 to 16.5%.

Интегрированная система анализа спектров полученных методом ЛИЭС для обеспечения качества измерений

To ensure the reliability of calculations of the parameters of the spectra obtained by various methods, a program was created for decomposing the spectra into Gaussian components in manual and automatic modes. Manual mode is used to determine the boundary conditions necessary for determining the global extremum. Next, an automatic mode is launched that provides rapid calculations of the spectrum parameters and determines their metrological characteristics, separating the value of the useful signal from the signals of the components, background and noise. The paper shows examples of separating the chromium signal from the signals of the components located on the right and left, as well as from the background signal and taking into account the noise level, which allows improving the analysis characteristics. Optimization of the program in order to determine the boundary parameters of the search for calculated parameters and its robustness is debugged by creating data similar to the experimental data using the "folding knife" or "BUTSTRAP" method.. Measurement quality is ensured by integrating experimental data with the capabilities of the SPECTRUM program. The SPECTRUM program is used as a database for metrological support of measurements and determination of reliability, expressiveness and cost-effectiveness of measurements. In examples 11 parameters: S1, S2, S3, M1, M2, M3, σ1, σ2, σ3, A, where S2 – the area of the useful signal; S1, S3 square harmful signals; M1, M2, M3 – wavelength signals; σ1, σ2, σ3 – half-width signals; A, B – parameters of background; I – noise level. Useful S2 signals depending on the chromium concentration are the basis for determining the calibration function and determining the metrological characteristics of both the calibration function and the analysis result.

Quantification of Minor Chemical Elements in Particulate Matter Collected from In-Use Diesel Engine Passenger Vehicles by Laser-Induced Breakdown Spectroscopy

This research qualitatively and quantitatively characterises the minor chemical elements in diesel particulate matter (DPM). DPM was extracted from in-use diesel engine passenger vehicles of diverse types and models from major brand car producers in Europe. We analysed particulate matter extracted from the exhaust manifold part from passenger vehicles that are used in daily life environment. To qualitatively and quantitatively characterise the DPM, we employed the high-resolution Laser-Induced Breakdown Spectroscopy analytical technique (LIBS). Qualitative spectrochemical LIBS analyses confirmed the presence of minor chemical elements—silicon, nickel, titan, potassium, strontium, and molybdenum in DPM. For quantification of the LIBS signal, the calibration functions were constructed from internal calibration standards. Different concentrations of detected minor elements Si, Ni, Ti, K, Sr, and Mo were measured with respect to the type of complex particulate matter.

Evaluating capacitive wetness sensors for measuring deposition in electrostatically charged spraying operations

Standard methods for measuring pesticide deposition include water sensitive paper and fibre (paper or cord) collectors, which require time consuming manual steps to gather, process and interpret results. Measurement of pesticide deposition is important in evaluating the efficacy of a spray, which affects the total crop yield. A lack of knowledge about spray quality often results in the need to spray to excess, which can contaminate the soil and damage neighbouring ecosystems and the atmosphere. The suitability of PHYTOS 31 capacitive leaf wetness sensors (Meter Group, Pullman, WA, USA) for spray sensing applications was analysed. The best fit calibration function for droplets of ~ 1 μL volume was linear (R2 = 0.985). The best fit calibration function for drops > 10 μL was a weighted sum of a linear and power function (R2 = 0.984). Thus, the calibration function should be chosen according to the anticipated size of droplet. The PHYTOS 31 sensors and water sensitive papers were used in a field test, comparing electrostatically charged and uncharged sprays. Both measurement techniques show that charged spray is more effective in covering parts of the plants which do not have a direct line of sight to the nozzle. The techniques disagree on quantitative coverage measurement, with the water sensitive papers reporting areal coverage two to four times higher than the capacitive sensors. High-speed video observations show that this is due to contraction (de-wetting) of the drop on the capacitive sensors. The surface of the capacitive sensors is more hydrophobic than the papers. The hydrophobicity of the capacitive sensors appears to be a better match to plant leaves than that of the papers. Capacitive sensors are a suitable measurement tool for evaluating liquid coverage in the field, but further calibration is necessary to be confident in the quantitative data.

Shear measurement bias

We present a new shear calibration method based on machine learning. The method estimates the individual shear responses of the objects from the combination of several measured properties on the images using supervised learning. The supervised learning uses the true individual shear responses obtained from copies of the image simulations with different shear values. On simulated GREAT3 data, we obtain a residual bias after the calibration compatible with 0 and beyond Euclid requirements for a signal-to-noise ratio &gt; 20 within ∼15 CPU hours of training using only ∼105 objects. This efficient machine-learning approach can use a smaller data set because the method avoids the contribution from shape noise. The low dimensionality of the input data also leads to simple neural network architectures. We compare it to the recently described method Metacalibration, which shows similar performances. The different methods and systematics suggest that the two methods are very good complementary methods. Our method can therefore be applied without much effort to any survey such as Euclid or the Vera C. Rubin Observatory, with fewer than a million images to simulate to learn the calibration function.

Selective detection of complex gas mixtures using point contacts: concept, method and tools.

Of all modern nanosensors using the principle of measuring variations in electric conductance, point-contact sensors stand out in having a number of original sensor properties not manifested by their analogues. The nontrivial nature of point-contact sensors is based on the unique properties of Yanson point contacts used as the sensing elements. The quantum properties of Yanson point contacts enable the solution of some of the problems that could not be solved using conventional sensors measuring conductance. In the present paper, we demonstrate this by showing the potential of quantum point-contact sensors to selectively detect components of a gas mixture in real time. To demonstrate the high efficiency of the proposed approach, we analyze the human breath, which is the most complex of the currently known natural gas mixtures with extremely low concentrations of its components. Point-contact sensors allow us to obtain a spectroscopic profile of the mixture. This profile contains information about the complete set of energy interactions occurring in the point contact/breath system when the breath constituents adsorb to and desorb from the surface of the point-contact conduction channel. With this information we can unambiguously characterize the analyzed system, since knowing the energy parameters is key to successfully identifying and modeling the physicochemical properties of various quantum objects. Using the point-contact spectroscopic profile of a complex gas mixture it is possible to get a functional dependence of the concentration of particular breath components on the amplitude of the sensor output signal. To demonstrate the feasibility of the proposed approach, we analyze the point-contact profiles from the breath of several patients and compare them with the concentrations of serotonin and cortisol in the body of each patient. The obtained results demonstrate that the proposed methodology allows one to get an effective calibration function for a non-invasive analysis of the level of serotonin and cortisol in the human body using the point-contact breath test. The present study indicates some necessary prerequisites for the design of fast detection methods using differential sensor analysis in real time, which can be implemented in various areas of science and technology, among which medicine is one of the most important.

A simulation comparison of calibration functions for different sets of spectral filter passbands in the traditional pure rotational Raman lidar technique

The accuracy of tropospheric temperature measurements with pure rotational Raman (PRR) lidars is affected by the collisional broadening of N2 and O2 PRR lines. In this paper, we intercompare nine calibration functions (CFs) in the traditional PRR lidar technique via simulation. Taking into account the PRR line broadening, the simulation is performed for five sets of spectral filters (SFs) with different passbands in a PRR lidar receiving system. For simplicity of calculations, the transmission function of each SF is approximated by a rectangular function on the wavenumber interval, within which a SF passes the bulk of the backscattered signal intensity in the corresponding PRR lidar channel. A narrow-linewidth laser operating at wavelengths of 354.67 and 532 nm is considered as a lidar transmitter. The CF best suited for tropospheric temperature retrievals from raw PRR lidar data for each set of SFs and laser wavelength is determined by comparative analysis of calibration errors ΔT produced using these CFs. The absolute error |ΔT| does not exceed the value of 3 × 10–3 K when using the best three-coefficient CF, while |ΔT| < 4 × 10–4 K for the best four-coefficient CF regardless of the laser wavelength and SF set used.

Design of Torque Standard Device for Extreme Environment

A torque standard device suitable for extreme environment is designed. The standard device transmits the torque value of calibrated torque sensor in extreme environment to normal temperature environment through torque transmission shaft to realize the calibration function. The mechanical design of the shaft of the device is carried out, and the error sources of the calibration device are analyzed, and the error distribution is carried out according to the technical indicators of the standard device. The calculation results show that the maximum allowable error of the standard device is 0.7Nm, which meets the calibration accuracy requirements of the extreme torque standard device.

Is the Time-Domain Reflectometry (TDR) Technique Suitable for Moisture Content Measurement in Low-Porosity Building Materials?

Measuring moisture content in building materials is essential both for professional practice and for research. However, this is a very complex task, especially when long-term minor destructive measurements are desired. The time-domain reflectometry (TDR) technique is commonly used for soil moisture measurements, but its application in construction materials is considered a relatively new method, particularly for low-porosity building materials. The major obstacles to its current use in construction materials are (1) the difficulty of ensuring good contact between the TDR probe and the material, and (2) the lack of appropriate conversion functions between the measured relative permittivity and the moisture content of building materials. This paper intends to contribute to overcoming these difficulties by explaining in detail all the required steps to monitor moisture content in real-scale limestone walls. For that, a device is presented to guarantee the correct installation of the TDR probes on the walls, and a calibration procedure through the gravimetric method is proposed to avoid the use of an unsuitable calibration function developed for soil moisture measurements. In addition, the importance of the individual probe calibration is discussed, as well as TDR advantages and disadvantages for construction materials. The results obtained so far reveal that the TDR technique is suitable to detect moisture content variations in limestone, which is a low-porosity building material.

A comprehensive calibrated phytolith based climatic index from the Himalaya and its application in palaeotemperature reconstruction

Past climate reconstructions from palaeoecological records require an understanding of relationships between modern vegetation and climate. Phytoliths are being used widely to reconstruct variations in C3/C4 grasses in the past vegetation and corresponding climate. However, little understanding is available on their relationships with the climate driver(s). Even though, the driver(s) regulating C3/C4 grass distributions vary regionally, while reconstructing the past distributions, a grass phytolith-based climatic index (Ic) has often been found to be used globally without assessing its regional consistency. In the Himalaya, the working potential of Ic has proven to be unsatisfactory when compared to other regions of the globe. To improve the efficacy of Ic, we have identified the redundant grass phytolith morphs and revised it by including four exclusive C3-grass indicator morphotypes (bilobate trapezoidal, bilobate scooped, saddle tall and saddle plateaued) to the existing Ic calculation. Thus, a new climatic index, revised Ic (rIc) is proposed in this article. We have compared the rIc with modern climate variables and a relationship with mean annual temperature (MAT) is established with statistical validation. To assess the working potential of the proposed calibration function in the past temperature reconstructions, we have estimated the late Holocene MAT variations in the Himalaya using rIc. We infer that in the mountainous regions like the Himalaya, even with irregular precipitation distribution, variability in C3/C4 grass distributions and their phytolith spectra seem to be a primary function of temperature. Further, we recommend that rIc can be satisfactorily used to reconstruct past temperature variations in the Himalaya and similar mountainous regions where soil water availability is not a limiting factor.

Uncertainty Estimations for Collision Cross Section Determination via Uniform Field Drift Tube-Ion Mobility-Mass Spectrometry.

Uniform field drift tube ion mobility-mass spectrometry (DTIM-MS) has emerged as a valuable tool for a range of analytical applications. In focus here are standardized collisional cross section values from DTIM-MS (DTCCS) as a candidate identification point for various analytical workflows. Of critical importance in establishing this parameter as a valid identification point is a rugged estimation of uncertainties according to the procedures used for their derivation. Relying on the assumption of the zero-field limit, the primary method of measurement for DTCCS values involves experimental determination of arrival times of an ion measured at several different field strengths transiting a drift tube filled with high purity drift gas, while a method using measurements of external calibrants at a single field strength is employed to allow for online measurements of transient signals (e.g., chromatographic peaks). Both approaches are here considered with respect to the uncertainty of input experimental variables (temperature, pressure, voltages, physical constants) and the steps of the calibration function employed. Estimations of uncertainty were performed according to EURACHEM with Monte Carlo simulations and reveal that existing consensus calibration standards from experimental stepped-field IM-MS determinations have estimated expanded uncertainties in the range of 2.7 to 4.6% (k = 2). Application of these standards for calibration considering these input uncertainties reveals uncertainty estimates of 4.7-9.1% (k = 2) for measured values using an established single-field calibration approach. Finally, directions for improving this situation via new experimental efforts toward standard reference and calibration materials are presented.