Exploring atmospheric radon with airborne gamma-ray spectroscopy

$^{222}$Rn is a noble radioactive gas produced along the $^{238}$U decay chain, which is present in the majority of soils and rocks. As $^{222}$Rn is the most relevant source of natural background radiation, understanding its distribution in the environment is of great concern for investigating the health impacts of low-level radioactivity and for supporting regulation of human exposure to ionizing radiation in modern society. At the same time, $^{222}$Rn is a widespread atmospheric tracer whose spatial distribution is generally used as a proxy for climate and pollution studies. Airborne gamma-ray spectroscopy (AGRS) always treated $^{222}$Rn as a source of background since it affects the indirect estimate of equivalent $^{238}$U concentration. In this work the AGRS method is used for the first time for quantifying the presence of $^{222}$Rn in the atmosphere and assessing its vertical profile. High statistics radiometric data acquired during an offshore survey are fitted as a superposition of a constant component due to the experimental setup background radioactivity plus a height dependent contribution due to cosmic radiation and atmospheric $^{222}$Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS $^{222}$Rn detection but also a (0.96 $\pm$ 0.07) Bq/m$^{3}$ $^{222}$Rn concentration and a (1318 $\pm$ 22) m atmospheric layer depth fully compatible with literature data.Comment: 17 pages, 8 figures, 2 table

The analysis of multichannel airborne gamma-ray spectra

The conventional processing of airborne gamma-ray spectrometric data uses 3 broad energy windows to estimate the ground concentrations of K U and Th. This thesis investigates the potential for using the full gamma-ray spectrum in an attempt to increase the amount of information currently extracted from airborne gamma-ray data. The observed spectrum is considered as the sum of 3 terrestrial and 3 background components. Given the shapes of the component spectra, the airborne gamma-ray spectrometric inverse problem is to determine the relative contributions of the components to the observed spectrum. The component spectra are determined through suitable airborne and ground calibrations. The limitations of the component spectra have necessitated a model-based approach to multichannel fitting. The components are fit to real data, and only those energies over which a good fit is achieved are used for multichannel processing. A parametric model based on a principal component analysis of the terrestrial component spectra as functions of simulated detector height is used to find the K, U and Th terrestrial component spectra that best fit the background-corrected airborne data. The simulated heights are mapped onto actual heights using airborne calibrations over a calibration range. This enables the terrestrial component spectra to be used for the calibration of multichannel background estimation methods. The component spectra are then fit to the background-corrected observed spectra to obtain elemental count rates. This strategy ensures the best possible fit between model and data, and minimizes the propagation of statistical errors in the observations into the estimates of the elemental count rates. The analysis of multichannel spectra using this model produces 3 new parameters - the effective height of the detector above K, U and Th sources. These effective heights may be useful for regolith mapping and for refining the data processing procedures. The multichannel processing results in significant reductions in the fractional errors associated with the estimated elemental count rates. For 3 surveys processed using the new methodology, the average deviations of the K, U and Th elemental count rates from the estimated mean elemental count rates at each observation point are reduced by 12.4%, 26.5% and 20.3%, respectively, when compared to the conventional 3-channel method. This results in a better structural resolution of small anomalies in enhanced images of the processed data

Similar Risk of Kidney Failure among Patients with Blinding Diseases Who Receive Ranibizumab, Aflibercept, and Bevacizumab:An Observational Health Data Sciences and Informatics Network Study

Purpose: To characterize the incidence of kidney failure associated with intravitreal anti-VEGF exposure; and compare the risk of kidney failure in patients treated with ranibizumab, aflibercept, or bevacizumab. Design: Retrospective cohort study across 12 databases in the Observational Health Data Sciences and Informatics (OHDSI) network. Subjects: Subjects aged ≥ 18 years with ≥ 3 monthly intravitreal anti-VEGF medications for a blinding disease (diabetic retinopathy, diabetic macular edema, exudative age-related macular degeneration, or retinal vein occlusion). Methods: The standardized incidence proportions and rates of kidney failure while on treatment with anti-VEGF were calculated. For each comparison (e.g., aflibercept versus ranibizumab), patients from each group were matched 1:1 using propensity scores. Cox proportional hazards models were used to estimate the risk of kidney failure while on treatment. A random effects meta-analysis was performed to combine each database's hazard ratio (HR) estimate into a single network-wide estimate. Main Outcome Measures: Incidence of kidney failure while on anti-VEGF treatment, and time from cohort entry to kidney failure. Results: Of the 6.1 million patients with blinding diseases, 37 189 who received ranibizumab, 39 447 aflibercept, and 163 611 bevacizumab were included; the total treatment exposure time was 161 724 person-years. The average standardized incidence proportion of kidney failure was 678 per 100 000 persons (range, 0–2389), and incidence rate 742 per 100 000 person-years (range, 0–2661). The meta-analysis HR of kidney failure comparing aflibercept with ranibizumab was 1.01 (95% confidence interval [CI], 0.70–1.47; P = 0.45), ranibizumab with bevacizumab 0.95 (95% CI, 0.68–1.32; P = 0.62), and aflibercept with bevacizumab 0.95 (95% CI, 0.65–1.39; P = 0.60). Conclusions: There was no substantially different relative risk of kidney failure between those who received ranibizumab, bevacizumab, or aflibercept. Practicing ophthalmologists and nephrologists should be aware of the risk of kidney failure among patients receiving intravitreal anti-VEGF medications and that there is little empirical evidence to preferentially choose among the specific intravitreal anti-VEGF agents. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.</p

Proof-of-Principle Experiment for FEL-Based Coherent Electron Cooling,”

Abstract Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, highintensity hadron-hadron and electron-hadron colliders. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using SRF linac. In this paper, we describe the setup for CeC installed into one of RHIC&apos;s interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC

Analysis of aqueous matrices using supercritical fluid extraction in conjunction with chromatographic, spectroscopic and mass spectometric techniques

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Atmospheric Radon in a marine environment: a novel approach based on airborne gamma-ray spectroscopy

222Rn is a naturally occurring noble gas produced via alpha decay of 226Ra and it is the only gaseous daughter product of the decay chain of 238U, a radioisotope present in the majority of soils and rocks. 222Rn is almost chemically inert, it exhales into the atmosphere and migrates by diffusion and convection: as it runs out mainly through radioactive decay characterized by a 3.82 days half-life, it is a widespread atmospheric tracer, particularly effective for gathering insights into air vertical mixing processes in the atmospheric boundary layer. Understanding 222Rn distribution in the environment is also of great concern for investigating the health impacts of low-level radioactivity and for supporting regulation of human exposure to ionizing radiation in modern society. Airborne Gamma-Ray Spectroscopy (AGRS) always treated 222Rn as a source of background: its decay product 214Bi is the main gamma-emitter in the 238U decay chain and, since it binds to airborne aerosols, it is responsible for the measured radon background. For the first time we exploit the AGRS method for quantifying the presence of 222Rn in the atmosphere and assessing its vertical profile. AGRS measurements have been performed in the (70 – 3000) m altitude range during a ~4 hours survey over the Tyrrhenian sea. The experimental setup, made up of four 4L NaI(Tl) crystals, was mounted on the Radgyro, a prototype aircraft designed for multisensorial acquisitions in the field of proximal remote sensing. A theoretical model accounting for the presence of atmospheric 222Rn has been developed in order to reconstruct experimental radiometric data over the entire altitude range: the overall count rate recorded in the 214Bi photopeak is fitted as a superposition of a constant component due to the radioactivity of the aircraft and of the equipment plus a height dependent contribution due to cosmic radiation and atmospheric 222Rn. Modeling the latter component requires a radon vertical profile, which is in turn directly connected with the dynamics of the atmospheric boundary layer. Thanks to the large elevation extent, it has been possible to explore the presence of radon in the atmosphere via the modeling of the count rate in the 214Bi photopeak energy window according to two analytical models which respectively exclude and account for the presence of atmospheric radon. The refined statistical analysis provides not only a conclusive evidence of AGRS 222Rn detection but also a (0.96 ± 0.07) Bq/m^3 222Rn concentration and a (1318 ± 22) m atmospheric layer depth fully compatible with literature data