Dosimetric accuracy of a cross-calibration coefficient for plane-parallel ionization chamber obtained in low-energy electron beams using various cylindrical dosimeters

Introduction: The accuracy of the cross-calibration procedure depends on ionization chamber type, both used as reference one and under consideration. Also, the beam energy and phantom medium could influence the precision of cross calibration coefficient, resulting in a systematic error in dose estimation and thus could influence the linac beam output checking. This will result in a systematic mismatch between dose calculated in treatment planning system and delivered to the patient. Material and methods: The usage of FC65-G, CC13 and CC01 thimble reference chambers as well as 6, 9, and 15 MeV electron beams has been analyzed. A plane-parallel PPC05 chamber was calibrated since scarce literature data are available for this dosimeter type. The influence of measurement medium and an effective point of measurement (EPOM) on obtained results are also presented. Results: Dose reconstruction precision of ~0.1% for PPC05 chamber could be obtained when cross-calibration is based on a thimble CC13 chamber. Nd,w,Qcross obtained in beam ≥ 9MeV gives 0.1 – 0.5% precision of dose reconstruction. Without beam quality correction, 15 MeV Nd,w,Qcross is 10% lower than Co-60 Nd,w,0. Various EPOM shifts resulted in up to 0.6% discrepancies in Nd,w,Qcross values. Conclusions: Ionization chamber with small active volume and tissue-equivalent materials supplies more accurate cross-calibration coefficients in the range of 6 – 15 MeV electron beams. In the case of 6 and 9 MeV beams, the exact position of an effective point of measurement is of minor importance. In-water cross-calibration coefficient can be used in a solid medium without loss of dose accuracy.

Arctic sea surface height maps from multi-altimeter combination

We present a new Arctic sea level anomaly dataset based on the combination of three altimeter missions using an optimal interpolation scheme. Measurements from SARAL/AltiKa, CryoSat-2 and Sentinel-3A are blended together, providing an unprecedented resolution for this type of product. Such high-resolution products are necessary to tackle some contemporaneous science questions in the basin. We use the adaptive retracker to process both open ocean and lead echoes on SARAL/AltiKa, thus removing the need to estimate a bias between open ocean and ice-covered areas. The usual processing approach, involving an empirical retracking algorithm on specular echoes, is applied on CryoSat-2 and Sentinel-3A synthetic aperture radar (SAR) mode echoes. SARAL/AltiKa also provides the baseline for the cross-calibration of CryoSat-2 and Sentinel-3A data. The final gridded fields cover all latitudes north of 50∘ N, on a 25 km EASE2 grid, with one grid every 3 d over 3 years from July 2016 to April 2019. When compared to tide gauge measurements available in the Arctic Ocean, the combined product exhibits a much better performance than mono-mission datasets with a mean correlation of 0.78 and a mean root-mean-square deviation (RMSd) of 5 cm. The effective temporal resolution of the combined product is 3 times better than a single mission analysis. This dataset can be downloaded from https://doi.org/10.24400/527896/a01-2020.001 (Prandi, 2020).

In situ cosmogenic ¹⁰Be in pyroxene with an application to surface exposure dating

<p>Cosmogenic nuclides are an important tool in quantifying many Earth-surface processes. Beryllium-10 (¹⁰Be) is commonly extracted out of the mineral quartz; however many landscapes lack quartz bearing rocks. In order to establish a new chronometer based on ¹⁰Be in pyroxene for use in New Zealand and Antarctica, it is necessary to verify cleaning protocols and determine a local production rate. In this study, I have tested and modified an existing pyroxene decontamination procedure in order to further develop the use of ¹⁰Be in pyroxene as a chronometer. This method successfully removes the meteoric component of ¹⁰Be in pyroxene, allowing only the concentration of in situ produced ¹⁰Be to be measured. Additionally, production rates for ¹⁰Be in pyroxene have been determined empirically for New Zealand using cross-calibration with measured ³He concentrations and an independent radiocarbon age of the Murimotu debris avalanche in the central North Island, New Zealand of 10.6 ± 1.1 ka. Theoretical ¹⁰Be pyroxene production rates were also determined, based on the composition of the Murimotu pyroxene. The best estimate for the 10Be pyroxene production rate is 3.4 ± 0.8 atoms g⁻¹ yr⁻¹ at sea-level high latitude, which was determined via cross-calibration with the radiocarbon age for the deposit. This work shows that production rates for ¹⁰Be in pyroxene are both empirically and theoretically 8-27% lower than in quartz. The ³He/¹⁰Be ratio in the Murimotu pyroxene is 34.5 ± 9.9; this is indistinguishable from global ³He-pyroxene/¹⁰Be-quartz production ratios. In a case study surface exposure ages were determined for bedrock samples and cobble erratics collected in a vertical transect on Mount Gran, Antarctica, by applying the aforementioned ¹⁰Be pyroxene decontamination procedure and radiocarbon derived production rates. A chronology for ice surface lowering was obtained for the adjacent Mackay Glacier, indicating the ice surface lowered approximately 60 m during a relatively rapid episode of thinning which occurred between ~13.5 ka and 11 ka. This thesis presents a successful test of decontamination procedures, new production rates, and an example application, showing the promise of ¹⁰Be in pyroxene as a chronometer. The development of ¹⁰Be in pyroxene allows environments without quartz-bearing rocks to be dated using this widely used nuclide. The pairing of ¹⁰Be with ³He in pyroxene would allow complex exposure histories to be determined, expanding the application.</p>

In situ cosmogenic ¹⁰Be in pyroxene with an application to surface exposure dating

<p>Cosmogenic nuclides are an important tool in quantifying many Earth-surface processes. Beryllium-10 (¹⁰Be) is commonly extracted out of the mineral quartz; however many landscapes lack quartz bearing rocks. In order to establish a new chronometer based on ¹⁰Be in pyroxene for use in New Zealand and Antarctica, it is necessary to verify cleaning protocols and determine a local production rate. In this study, I have tested and modified an existing pyroxene decontamination procedure in order to further develop the use of ¹⁰Be in pyroxene as a chronometer. This method successfully removes the meteoric component of ¹⁰Be in pyroxene, allowing only the concentration of in situ produced ¹⁰Be to be measured. Additionally, production rates for ¹⁰Be in pyroxene have been determined empirically for New Zealand using cross-calibration with measured ³He concentrations and an independent radiocarbon age of the Murimotu debris avalanche in the central North Island, New Zealand of 10.6 ± 1.1 ka. Theoretical ¹⁰Be pyroxene production rates were also determined, based on the composition of the Murimotu pyroxene. The best estimate for the 10Be pyroxene production rate is 3.4 ± 0.8 atoms g⁻¹ yr⁻¹ at sea-level high latitude, which was determined via cross-calibration with the radiocarbon age for the deposit. This work shows that production rates for ¹⁰Be in pyroxene are both empirically and theoretically 8-27% lower than in quartz. The ³He/¹⁰Be ratio in the Murimotu pyroxene is 34.5 ± 9.9; this is indistinguishable from global ³He-pyroxene/¹⁰Be-quartz production ratios. In a case study surface exposure ages were determined for bedrock samples and cobble erratics collected in a vertical transect on Mount Gran, Antarctica, by applying the aforementioned ¹⁰Be pyroxene decontamination procedure and radiocarbon derived production rates. A chronology for ice surface lowering was obtained for the adjacent Mackay Glacier, indicating the ice surface lowered approximately 60 m during a relatively rapid episode of thinning which occurred between ~13.5 ka and 11 ka. This thesis presents a successful test of decontamination procedures, new production rates, and an example application, showing the promise of ¹⁰Be in pyroxene as a chronometer. The development of ¹⁰Be in pyroxene allows environments without quartz-bearing rocks to be dated using this widely used nuclide. The pairing of ¹⁰Be with ³He in pyroxene would allow complex exposure histories to be determined, expanding the application.</p>

Integrated Geomechanical Modeling and Hydraulic Fracturing Design: From Particular Cases to the Overall Result

Objective and scope The objective of the work is to present an adequate workflow for conditioning geomechanical data and hydraulic fracturing design, adjustment and simultaneous verification of a MEM and hydraulic fracture models. These approaches are relevant for greenfields and also can be used when changing field development systems: from vertical fracked wells to a system of horizontal wells with multistage fracs. Methods, techniques, and process description The paper provides examples of issues in hydraulic fracturing planning due to poor attention to the reliability and robustness of geomechanical data. Given the critically of data quality, the authors describe a holistic approach used in collecting, analysing and conditioning data for building a MEM (1D; if necessary, 3D) as the basis of a frac design. Mini-frac is considered not only as a tool for setting the hydraulic fracturing design parameters, but also as a source of data for cross-calibration between the MEM and the hydraulic fracture models. Case studies of various HF models will demonstrate the influence of MEM-and-frac uncertainties and the tools for considering them in practical HF modelling. An approach to systematic clustering of input data for HF designs is described. The importance of measuring the fracture heights is stressed as a source of data for cross-calibration of HF and GM models. Results and conclusions The correct sequence of work, data consolidation and successive data refinement helps to maintain the database of elastic and strength properties of various target reservoirs, which proves the demand for core analysis and well logging, as well as geomechanical modelling. The improved quality of HF designs leads to better reliability of forecasts and proposed field development and individual wellwork strategies. The close integration of GM studies and modelling with HF design building enhances the operation culture, accelerates and streamlines the HF model build and validation processes, which can be a pace-setting experience for other oil and gas industries that are GM data users. Novelty and achievements The TNNC and RN-CEPiTR teams work in close cooperation and provide GM and HF integration to assess the fracture height in the target reservoirs at the Company's assets in order to improve the quality of HF modelling. The uncertainty influence on the HF design is reducing, so as the risks of screen-out and the risks of breakthrough into undesirable zones. The approach streamlines the engineering support for the hydraulic fracturing activity and understanding of the fracture parameters as the operations move from single-stage hydraulic fracturing to the optimized field development using horizontal wells with multi-stage hydraulic fracturing.

Physics informed deep learning to super-resolve and cross-calibrate solar magnetograms

Super-resolution techniques aim to increase the resolution of images by adding detail. Compared to upsampling techniques reliant on interpolation, deep learning-based approaches learn features and their relationships across the training data set to leverage prior knowledge on what low resolution patterns look like in higher resolution images. As an added benefit, deep neural networks can learn the systematic properties of the target images (i.e.\ texture), combining super-resolution with instrument cross-calibration. While the successful use of super-resolution algorithms for natural images is rooted in creating perceptually convincing results, super-resolution applied to scientific data requires careful quantitative evaluation of performances. In this work, we demonstrate that deep learning can increase the resolution and calibrate space- and ground-based imagers belonging to different instrumental generations. In addition, we establish a set of measurements to benchmark the performance of scientific applications of deep learning-based super-resolution and calibration. We super-resolve and calibrate solar magnetic field images taken by the Michelson Doppler Imager (MDI; resolution ~2"/pixel; science-grade, space-based) and the Global Oscillation Network Group (GONG; resolution ~2.5"/pixel; space weather operations, ground-based) to the pixel resolution of images taken by the Helioseismic and Magnetic Imager (HMI; resolution ~0.5"/pixel; last generation, science-grade, space-based).

Spectral Reflectance Estimation of UAS Multispectral Imagery Using Satellite Cross-Calibration Method

This paper introduces a satellite-based cross-calibration (SCC) method for spectral reflectance estimation of unmanned aircraft system (UAS) multispectral imagery. The SCC method provides a low-cost and feasible solution to convert high-resolution UAS images in digital numbers (DN) to reflectance when satellite data is available. The proposed method is evaluated using a multispectral data set, including orthorectified KHawk UAS DN imagery and Landsat 8 Operational Land Imager Level-2 surface reflectance (SR) data over a forest/grassland area. The estimated UAS reflectance images are compared with the National Ecological Observatory Network's imaging spectrometer (NIS) SR data for validation. The UAS reflectance showed high similarities with the NIS data for the near-infrared and red bands with Pearson's r values being 97 and 95.74, and root-mean-square errors being 0.0239 and 0.0096 over a 32-subplot hayfield.

Cross-Calibration of Bone Mineral Densities and Body Composition between GE Lunar Prodigy and Osteosys Primus

Background: The aim of this study was to investigate the correlation between bone mineral density (BMD) and body composition measured by the Osteosys Primus® and the GE Lunar Prodigy® and to calculate the conversion rate between the 2 devices.Methods: The 40 subjects were men and women in aged 20 to 29 years old. All participants were scanned twice on both the Osteosys Primus (OsteoSys) and the GE Lunar Prodigy (GE Healthcare) DXA systems using the manufacturers’ standard scanning and positioning protocols.Results: Compared to the GE Lunar device, the mean Osteosys fat mass was overestimated to be 12.1% (1,776.9 g) in the whole body, 5.1% (163.9 g) in gynoid, and 6.7% (87.2 g) in android. Compared with the GE Lunar device, the mean BMDs of the Osteosys Primus were underestimated to be 2.3% (0.023 g/cm2) in the whole body and 3.1% (0.035 g/cm2) in L1-4. Compared with the GE Lunar device, the mean lean mass derived by the Osteosys Primus were underestimated to 2.3% (1,045.3 g) in the total body, 3.8% (179.4 g) in arms, and 7.7% (1,104.8 g) in legs, respectively. There were a strong correlation of BMD and body composition between both groups.Conclusions: Linear correction equations were developed to ensure comparability of BMD and muscle mass between the Osteosys Primus and the GE Lunar Prodigy. Importantly, use of equations from previous studies would have increased the discrepancy between the Osteosys Primus and the GE Lunar Prodigy.