Point Source Research Articles

Ensuring the Safety of an Extraction Well from an Upgradient Point Source of Pollution in a Computationally Constrained Setting

Shallow groundwater is an important resource, especially in low- and middle-income countries; however, shallow groundwater is particularly vulnerable to point sources of pollution such as latrines or unlined waste disposal ponds. The objective of this paper is to derive a quantitative criterion for siting an extraction well and an upgradient point source of pollution to ensure that they are hydraulically disconnected, i.e., that no water flows from the point source to the well. To achieve this objective, we modeled the flow of shallow groundwater considering uniform regional flow, a single point source of pollution, and a single extraction well. For any set of flow rates and upgradient point source distance, we sought the minimum “off-center distance” ymin (i.e., the distance in the direction perpendicular to regional flow) that ensures the well and the point source are hydraulically disconnected. For constituencies with access to computing resources and coding expertise, we used a computer-based method for determining ymin that is exact to within the accuracy of a root-finding algorithm; this approach is recommended when computer access is available. For constituencies lacking these resources, we determined a simple, closed-form, approximate solution for ymin that has an average error of less than 3% for the conditions we tested. For a subset of scenarios in which the point source is sufficiently far upgradient of the well (n = 77), the root mean square relative error of the approximate solution is only 0.52%. We found that ymin depends on a length parameter (Qw + Qps)/QR, where Qw is the extraction rate of the well, Qps is the injection rate of the point source, and QR is the regional groundwater flow rate per unit of perpendicular length. Either the exact solution or the closed-form approximation can help to site wells near point sources of pollution, or to site point sources near wells, in a manner that protects the health of the well user. The approximate solution is valuable because many constituencies that rely on shallow wells for water supply and latrines for sanitation also lack access to the computer resources necessary to apply the exact solution.

An integrated experimental-modeling approach to identify key processes for carbon mineralization in fractured mafic and ultramafic rocks.

Controlling atmospheric warming requires immediate reduction of carbon dioxide (CO2) emissions, as well as the active removal and sequestration of CO2 from current point sources. One promising proposed strategy to reduce atmospheric CO2 levels is geologic carbon sequestration (GCS), where CO2 is injected into the subsurface and reacts with the formation to precipitate carbonate minerals. Rapid mineralization has recently been reported for field tests in mafic and ultramafic rocks. However, unlike saline aquifers and depleted oil and gas reservoirs historically considered for GCS, these formations can have extremely low porosities and permeabilities, limiting storage volumes and reactive mineral surfaces to the preexisting fracture network. As a result, coupling between geochemical interactions and the fracture network evolution is a critical component of long-term, sustainable carbon storage. In this paper, we summarize recent advances in integrating experimental and modeling approaches to determine the first-order processes for carbon mineralization in a fractured mafic/ultramafic rock system. We observe the critical role of fracture aperture, flow, and surface characteristics in controlling the quantity, identity, and morphology of secondary precipitates and present where the influence of these factors can be reflected in newly developed thermo-hydro-mechanical-chemical models. Our findings provide a roadmap for future work on carbon mineralization, as we present the most important system components and key challenges that we are overcoming to enable GCS in mafic and ultramafic rocks.

Hydrocarbon Traps for the Air Intake System: Component Test Rig and SHED Test Procedure for Determining Their Efficiencies

Hydrocarbon traps in the air intake system (AIS) are a common method for controlling evaporative emissions from the air intake path. Several different systems are available, but there is no standard method for determining their efficiencies. Therefore, a component test rig for hydrocarbon traps was developed. Some optimizations were necessary to achieve emission characteristics observed in engine measurements. Using this setup, several measurements were performed on four different hydrocarbon traps. The results were in reasonable agreement with those from engine measurements. Two different hydrocarbon (HC) traps were selected for further studies. In these studies, the repeatability and the dependency of the emission mass level were investigated. Furthermore, the hydrocarbon concentration in the air filter box was determined using point source flame ionization detector (FID) sampling and a metal oxide semiconductor (MOS) sensor. The data showed a correlation with the emission mass determined in a sealed housing emission determination (SHED) test.

The intrinsic distribution of Lyman-alpha halos

The emission and escape of Lyman-alpha photons from star-forming galaxies is determined through complex interactions between the emitted photons and a galaxy's interstellar and circumgalactic gas.\ This causes Lyman-alpha emitters (LAEs) to commonly appear not as point sources but in spatially extended halos with complex spectral profiles. We developed a 3D spatial-spectral model of Lyman-alpha halos (LAHs) to replicate LAH observations in integral field spectroscopic studies, such as those made with VLT/MUSE. The profile of this model is a function of six key halo properties: the halo- and compact-source exponential scale lengths sH $ and $r_ sC $), the halo flux fraction ($f_H$), the compact component ellipticity ($q$), the spectral line width (sigma ), and the spectral line skewness parameter (gamma ). Placing a series of model LAHs into datacubes that reflect observing conditions in the MUSE UDF-Mosaic survey, we tested their detection recoverability and determine that sigma , $r_ sH $, and $f_H$ are expected to have the most significant effect on the detectability of the overall LAH at a given central wavelength and intrinsic line luminosity. We developed a general selection function model that spans a grid of these halo parameters. Using it with a sample of 145 LAHs with measured halo properties observed in the UDF-Mosaic survey, we derived completeness-corrected, intrinsic distributions of the values of sigma , $r_ sH $, and $f_H$ for $3<z<5$ LAHs. We present the best-fit functional forms of the distributions as well as a sigma distribution corrected for instrumental line-spread function broadening, and thereby show the physical line-spread distribution of the intrinsic population. Finally, we discuss possible implications for these distributions for the nature of Lyalpha emission through the circumgalactic medium, finding that observations may undercount LAHs with extended halo scale lengths compared to the intrinsic population.

A spherical source distribution method for calculating acoustic radiation of elastic underwater structures

In this paper, a spherical source distribution method is established, and two kinds of spherical sound sources of symmetric and antisymmetric, distributed on a line inside the structure are proposed, in order to realize the vibro-acoustic calculation of three-dimensional elastic underwater structure. The spherical source distribution method has strong applicability and is suitable for the case where the shape of the structure is not axisymmetric. This method is a new method, and its fundamental formula is similar to the traditional acoustic boundary integral method, but it also has obvious differences. In numerical calculation, the traditional boundary element method is to divide the surface elements on the wet surface of the object, and transform the three-dimensional acoustic problem into the two-dimensional discrete element problem to solve. However, the spherical source distribution method, whose source points are only distributed on a straight line inside the object, transforms the three-dimensional acoustic problem into the quasi-one-dimensional discrete element problem, which makes the complexity and computation amount of the whole programming significantly reduced. In this paper, the fundamental principle of the spherical source distribution method, the calculation formula and the verification results of several numerical examples are discussed.

Carbon management technology pathways for reaching a U.S. Economy-Wide net-Zero emissions goal

The Carbon Management Study Group of the 37th Energy Modeling Forum (EMF 37) designed seven scenarios to explore the role of three potentially key technology suites – point source carbon dioxide capture and storage (PSCCS), direct air capture of carbon dioxide (DACCS), and hydrogen systems (H2) – in shaping the broader technology pathways to reaching net-zero carbon dioxide (CO2) emissions in United States by 2050. Each scenario was run by up to 13 models participating in the EMF 37 study. Results show that carbon dioxide removal technologies were consistently a major part of successful pathways to net-zero U.S. CO2 emissions in 2050. Achieving this net-zero CO2 goal without any form of carbon dioxide capture and storage was found to be impossible for most models; some models also found it impossible to reach net-zero without DACCS. The marginal cost of achieving net-zero CO2 emissions in 2050 was between two and 10 times higher without PSCCS and/or DACCS available. The carbon price at which DACCS was deployed as a backstop technology depended upon the assumed cost at which DACCS was available at scale. Carbon prices were between $250 and $500 per ton CO2 when DACCS deployed as a backstop. The average CO2 capture rate across all models in 2050 in the central net-zero scenario was 1.3 GtCO2/year, which implies a substantial upscaling of capacity to move and store CO2. Hydrogen sensitivity scenarios showed that H2 typically constituted a relatively small share of the overall U.S. energy system; however, H2 deployed in applications that are considered hard to decarbonize, facilitating transition towards net-zero emissions.

Investigative photometry experiments on planar extended-light sources

The inverse-square decay law of the illuminance of a point light source with distance is a common notion of basic optics theory, which is readily demonstrated to be a direct consequence of the propagation of spherical wave fronts with the centre at the light source. It is far less common to address the experimental verification of this law and, even less, to study the illuminance decay with the distance of extended light sources, which somehow represent an unknown topic. We propose a scientific experiment where the light sensor of a smartphone is used to collect illuminance data as a function of the source-to-sensor distance and orientation. Through this procedure, students can realize the limit of validity of the inverse-square law and determine the luminance flux of the chosen point-like light source (e.g. the white LED flashlight of a smartphone). More interestingly, when dealing with extended sources (e.g. the LCD of a laptop displaying a white image) subtle characteristics of the decay trend emerge, particularly for distances lower that the source size. A detailed analysis of these characteristics is presented though a process allowing student engagement in a real scientific investigation, envisaging steps of data acquisition through experimental measurements, model construction on the basis of the observed patterns, and finally model testing. We provide a guided formulation for the general modelling of planar emitters, starting from the theoretical treatment of Lambertian sources. In this way, students are able to quantify the luminous emission also for extended sources and their deviation from a Lambertian behaviour.

Impact of extragalactic point sources on the low-frequency sky spectrum and cosmic dawn global 21-cm measurements

Abstract Contribution of resolved and unresolved extragalactic point sources to the low-frequency sky spectrum is a potentially non-negligible part of the astrophysical foregrounds for cosmic dawn 21-cm experiments. The clustering of such point sources on the sky, combined with the frequency-dependence of the antenna beam, can also make this contribution chromatic. By combining low-frequency measurements of the luminosity function and the angular correlation function of extragalactic point sources, we develop a model for the contribution of these sources to the low-frequency sky spectrum. Using this model, we find that the contribution of sources with flux density >10−6 Jy to the sky-averaged spectrum is smooth and of the order of a few kelvins at 50–200 MHz. We combine this model with measurements of the galactic foreground spectrum and weigh the resultant sky by the beam directivity of the conical log-spiral antenna planned as part of the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) project. We find that the contribution of point sources to the resultant spectrum is $\sim 0.4\%$ of the total foregrounds, but still larger by at least an order of magnitude than the standard predictions for the cosmological 21-cm signal. As a result, not accounting for the point-source contribution leads to a systematic bias in 21-cm signal recovery. We show, however, that in the REACH case, this reconstruction bias can be removed by modelling the point-source contribution as a power law with a running spectral index. We make our code publicly available as a Python package labelled epspy.

HEV-3 subtypes and strains detected in cases of HEV infection in central Italy from 2015 to 2023.

HEV is an emerging pathogen in Europe and was previously shown to be hyperendemic in areas of Abruzzo and Lazio, Central Italy. No systematic analysis of the HEV strains responsible for human infections over several years in Central Italy has previously been reported. Aim of the study was the molecular characterization of HEV from autochthonous hepatitis E cases occurred in Abruzzo and Lazio between 2015 and 2023. Samples from 118 cases collected as part of virological surveillance in Abruzzo and Lazio from 2015 to 2023 were subjected to HEV sequencing and phylogenetic analysis. The main observed subtype was 3f, followed by 3c and 3e. The annual subtype distribution was quite stable over the observation period, but 3f cases tended to concentrate in winter/early spring whereas 3e cases in summer. Phylogenetic clusters of highly related sequences (a) highlighted unrecognized "point source outbreaks", (b) provided molecular support to temporally and/or geographically linked cases and (c) provided evidence for transmission of identical/highly related strains up to months/years following their first detection. The data provide an overview of the HEV strains responsible for human infections over eight years in Central Italy. The observed subtype distribution appears to agree better with the subtype distribution reported in Italy in pigs rather than in geographically matched wild boars, suggesting pig and its derivate food was a more frequent source of infection than wild boar in Abruzzo and Lazio. Molecular characterization is essential to recognize "point source outbreaks" and to monitor HEV circulation.

On the implementation of acollinearity in PET Monte Carlo simulations

Objective.Acollinearity of annihilation photons (APA) introduces spatial blur in positron emission tomography (PET) imaging. This phenomenon increases proportionally with the scanner diameter and it has been shown to follow a Gaussian distribution. This last statement can be interpreted in two ways: the magnitude of the acollinearity angle, or the angular deviation of annihilation photons from perfect collinearity. As the former constitutes the partial integral of the latter, a misinterpretation could have significant consequences on the resulting spatial blurring. Previous research investigating the impact of APA in PET imaging has assumed the Gaussian nature of its angular deviation, which is consistent with experimental results. However, a comprehensive analysis of several simulation software packages for PET data acquisition revealed that the magnitude of APA was implemented as a Gaussian distribution.Approach.We quantified the impact of this misinterpretation of APA by comparing simulations obtained with GATE, which is one of these simulation programs, to an in-house modification of GATE that models APA deviation as following a Gaussian distribution.Main results.We show that the APA misinterpretation not only alters the spatial blurring profile in image space, but also considerably underestimates the impact of APA on spatial resolution. For an ideal PET scanner with a diameter of 81 cm, the APA point source response simulated under the first interpretation has a cusp shape with 0.4 mm FWHM. This is significantly different from the expected Gaussian point source response of 2.1 mm FWHM reproduced under the second interpretation.Significance.Although this misinterpretation has been found in several PET simulation tools, it has had a limited impact on the simulated spatial resolution of current PET scanners due to its small magnitude relative to the other factors. However, the inaccuracy it introduces in estimating the overall spatial resolution of PET scanners will increase as the performance of newer devices improves.

Constructing a measurement-based spatially explicit inventory of US oil and gas methane emissions (2021)

Abstract. Accurate and comprehensive quantification of oil and gas methane emissions is pivotal in informing effective methane mitigation policies while also supporting the assessment and tracking of progress towards emissions reduction targets set by governments and industry. While national bottom-up source-level inventories are useful for understanding the sources of methane emissions, they are often unrepresentative across spatial scales, and their reliance on generic emission factors produces underestimations when compared with measurement-based inventories. Here, we compile and analyze previously reported ground-based facility-level methane emissions measurements (n=1540) in the major US oil- and gas-producing basins and develop representative methane emission profiles for key facility categories in the US oil and gas supply chain, including well sites, natural-gas compressor stations, processing plants, crude-oil refineries, and pipelines. We then integrate these emissions data with comprehensive spatial data on national oil and gas activity to estimate each facility's mean total methane emissions and uncertainties for the year 2021, from which we develop a mean estimate of annual national methane emissions resolved at 0.1° × 0.1° spatial scales (∼ 10 km × 10 km). From this measurement-based methane emissions inventory (EI-ME), we estimate total US national oil and gas methane emissions of approximately 16 Tg (95 % confidence interval of 14–18 Tg) in 2021, which is ∼ 2 times greater than the EPA Greenhouse Gas Inventory. Our estimate represents a mean gas-production-normalized methane loss rate of 2.6 %, consistent with recent satellite-based estimates. We find significant variability in both the magnitude and spatial distribution of basin-level methane emissions, ranging from production-normalized methane loss rates of < 1 % in the gas-dominant Appalachian and Haynesville regions to > 3 %–6 % in oil-dominant basins, including the Permian, Bakken, and the Uinta. Additionally, we present and compare novel comprehensive wide-area airborne remote-sensing data and results for total area methane emissions and the relative contributions of diffuse and concentrated methane point sources as quantified using MethaneAIR in 2021. The MethaneAIR assessment showed reasonable agreement with independent regional methane quantification results in sub-regions of the Permian and Uinta basins and indicated that diffuse area sources accounted for the majority of the total oil and gas emissions in these two regions. Our assessment offers key insights into plausible underlying drivers of basin-to-basin variabilities in oil and gas methane emissions, emphasizing the importance of integrating measurement-based data when developing high-resolution spatially explicit methane inventories in support of accurate methane assessment, attribution, and mitigation. The high-resolution spatially explicit EI-ME inventory is publicly available at https://doi.org/10.5281/zenodo.10734299 (Omara, 2024).

Demonstration of in-vivo simultaneous 3D imaging with 18F-FDG and Na131I using Compton–PET system

Simultaneous imaging of the SPECT tracer 131I and PET tracer 18F is important in the diagnosis of high- and low-grade thyroid cancers because high-grade thyroid cancers have high 18F-FDG and low 131I uptake, while low-grade thyroid cancers have high 131I and low 18F-FDG uptake. In this study, Na131I and 18F-FDG were simultaneously imaged using the Compton-PET system, in vivo. The angular resolution and sensitivity of the Compton camera with 356 keV gamma ray measured using a 133Ba point source were 12.3° and 2 × 10−5, respectively. The spatial resolution and sensitivity of PET were measured with a 22Na point source. The transaxial and axial spatial resolutions of the PET at the center of the FOV were 1.15 mm and 2.04 mm, respectively. Its sensitivity was 1.2 × 10−4. In-vivo images of the 18F and 131I isotopes were simultaneously acquired from mice. These showed that 18F-FDG was active in the heart, brown fat, and brain, while Na131I was active in the thyroid, stomach, and bladder. Artifacts were found in the Compton camera images when the activity of 131I was much lower than that of 18F. This study demonstrates the potential of simultaneous clinical imaging of 18F and 131I.

Radioxenon beta-gamma coincidence efficiency for a SAUNA detector by Geant4 simulation

A simulation for SAUNA II detector was carried out using the GEANT4 platform. The results demonstrated the accuracy of the simulation, which was well consistent with the experimental results. The simulation was used to calculate the coincidence detection efficiency of each radioxenon isotope, as well as to calculate the resolution for conversion electron peaks. Furthermore, using a 137Cs point source, the simulation was also utilized to perform the beta detector calibration procedure in two scenarios: first, the 137Cs was placed close to the middle of the plastic scintillator, and second, the 137Cs was placed outside the NaI(Tl) detector. The results showed that the spectrum in the first case is better; the source is closer to the plastic detector, leading to maximum Compton scattering. In the second case, a line in the spectrum disappears, so a high-intensity source is needed. Several methods exist to determine the coincidence detection efficiency of the detector. The recommended approach is to determine the total detection efficiency for different regions of interest. The simulation was also used to investigate the effect of replacing helium with nitrogen as a xenon-carrier gas, with the nitrogen resulting in a slight improvement in coincidence detection efficiencies and conversion electron resolution.

Calibration of a gamma ray Compton camera for radioactivity measurements

AbstractA dual-plane Compton imaging detector previously developed for prompt gamma imaging has been further tested and calibrated for quantitative radioactivity determination, specifically to assess radioactive debris from a reactor fuel element. The debris piece contains uranium isotopes and several long-lived fission products, including cesium-137 (Cs-137). The detector consists of two pixelated planes of cadmium-zinc-telluride (CZT) crystals which record gamma ray events interacting within these volumes. In addition to the energy spectrum obtained by pulse height analysis, the time-stamped events from each detector pixel are sorted by location into 3 categories for post-processing: intra-plane, inter-plane, and coincidence. An image reconstruction software enables spatial localization of the select gamma ray peak(s) from the spectrum, thereby separating the gamma ray by specific isotopes. We used the camera to image a small piece of debris for demonstration purposes. A measurement was performed alongside a high purity germanium (HPGe) detector, which could determine the isotopes' absolute activities and be used as a reference for the camera. In addition, a known isotopic point source was used to calibrate the camera’s energy detection efficiency in the same measurement geometry, correlating the image pixel intensity to the isotopic activity.

Tempo-spatial Variations in Nitrogen and Phosphorus Loads in Jianli-Hankou Reach of the Middle Yangtze River During the Past 20 Years

Ammonia nitrogen （NH4+-N） and total phosphorus （TP） were the major control pollutants in the Yangtze River Basin. Based on measured data from 2003 to 2020, the temporal and spatial variations in concentrations and fluxes of NH4+-N and TP in the Jianli to Hankou （JL-HK） reach of the Middle Yangtze River were studied, and the impacts of flow-sediment factors, tributary inflows, and others on variations in NH4+-N and TP fluxes were discussed. The results showed that： ① In recent years, NH4+-N and TP concentrations in the mainstream have declined significantly, with annual NH4+-N and TP concentrations at each monitoring station in 2020 averagely decreasing by 41% and 34% compared to those in 2003, respectively. Spatially, NH4+-N and TP concentrations decreased and then increased along the mainstream. NH4+-N and TP concentrations of tributary inflows, which include the Dongting Lake and Han River, were generally lower than that of the mainstream. The multi-year average values of NH4+-N and TP concentrations were both averaged at 0.12 mg·L-1 in the mainstream and were averaged at 0.11 mg·L-1 and 0.09 mg·L-1 in the tributary inflows. ② The flux differences between the upper and lower sections net of tributary confluences showed that NH4+-N and TP fluxes were lost in the Jianli to Luoshan （JL-LS） sub-reach and increased in the Luoshan to Hankou （LS-HK） sub-reach in most years. NH4+-N and TP fluxes decreased in the JL-LS sub-reach, which was related to the lower NH4+-N and TP concentrations in lateral inflows, such as Dongting Lake, and thus lowered the NH4+-N and TP concentrations in the mainstream. The LS-HK sub-reach showed the opposite trends, and the water and sediment loads increased in this sub-reach. Across the whole JL-HK reach, TP flux as well as water and sediment loads were recharged along the reach, whereas NH4+-N flux was reduced greatly, which could be attributed to the pollution abatement conducted in the Yangtze River Basin, which mainly focused on NH4+-N. ③ The correlation analysis results showed that NH4+-N fluxes had the strongest correlation with NH4+-N concentrations but not significantly correlated with discharges and sediment transport rates, indicating that NH4+-N was mainly controlled by point source pollution in the study reach. TP fluxes had higher correlations with discharges and sediment transport rates in high flow level periods, and the correlations between TP fluxes and TP concentrations were better in low flow level periods, reflecting that point source pollution contributed more to TP in dry seasons compared to flood seasons.

Design Optimisation of a Flat-Panel, Limited-Angle TOF-PET Scanner: A Simulation Study.

In time-of-flight positron emission tomography (TOF-PET), a coincidence time resolution (CTR) below 100 ps reduces the angular coverage requirements and, thus, the geometric constraints of the scanner design. Among other possibilities, this opens the possibility of using flat-panel PET detectors. Such a design would be more cost-accessible and compact and allow for a higher degree of modularity than a conventional ring scanner. However, achieving adequate CTR is a considerable challenge and requires improvements at every level of detection. Based on recent results in the ongoing development of optimised TOF-PET photodetectors and electronics, we expect that within a few years, a CTR of about 75 ps will be be achievable at the system level. In this work, flat-panel scanners with four panels and various design parameters were simulated, assessed and compared to a reference scanner based on the Siemens Biograph Vision using NEMA NU 2-2018 metrics. Point sources were also simulated, and a method for evaluating spatial resolution that is more appropriate for flat-panel geometry is presented. We also studied the effects of crystal readout strategies, comparing single-crystal and module readout levels. The results demonstrate that with a CTR below 100 ps, a flat-panel scanner can achieve image quality comparable to that of a reference clinical scanner, with considerable savings in scintillator material.

The role of soil amendments in limiting the leaching of agrochemicals: Laboratory assessment for copper sulphate and dicamba

Agriculture is among the major contributors to soil and groundwater pollution, primarily through the widespread leaching of pesticides and fertilizers from crops, as well as accidental releases from point sources. Therefore, alongside restrictions on the use of highly soluble agrochemicals and enhanced application guidelines, there is a significant demand for low-impact and cost-effective solutions aimed at reducing the mobility of agrochemicals in the soils. This study evaluates the potential of soil amendments—commonly used to enhance soil structural properties, water holding capacity, and fertility—to also absorb highly soluble pesticides, thereby controlling their leaching into the subsoil. Specifically, zeolite, biochar, and milled corncob were examined in laboratory tests under static (batch tests) and dynamic (column leaching tests) conditions to assess their effectiveness in adsorbing two widely used pesticides, copper sulphate and dicamba. Batch adsorption tests were performed using the amendments as pure materials and in mixtures with sand at various application rates (1–20% by weight). The highest affinity to copper sulphate was recorded for biochar, while dicamba exhibited a higher affinity to corncob, thanks to its higher content of organic carbon. Column leaching tests, performed at an amendment application rate of 5%, confirmed the different affinity observed in batch tests among pesticides and amended soil. Less than 2% of copper sulphate leached out from biochar- and zeolite-sand columns, while a recovery of 10% and 56% was observed for the corncob-sand mixture and for pure sand, respectively. Dicamba leaching from biochar- and corncob-sand columns was halved compared to pure sand. In conclusion, the tested soil amendments resulted highly effective in reducing pesticide leaching, opening the way for their possible applications in agriculture to reduce or prevent both diffuse and punctual contamination.

Rapid Fatality Estimates after Earthquakes in Western Mediterranean Countries for First Response

ABSTRACT The quality and speed of the current earthquake fatality estimates in Italy, Greece, Spain, Morocco, and Algeria by Quake Loss Assessment for Response and Mitigation (QLARM) is analyzed. The positive conclusion is that all investigated major earthquake disasters have been recognized as red alerts. In all but one of the tests, the range of estimated fatalities bracketed the number of finally reported fatalities. In five out of nine test earthquakes, the range of likely fatalities was calculated in real time, that is, within minutes after the respective earthquakes. These earthquakes occurred during the last 20 yr and only the minimal information of point sources was available. Additional four tests were performed for fatal earthquakes that occurred in the twentieth century and for which magnitudes and extents of the ruptures are known. The negative conclusions are: (1) locations and properties of critical facilities, such as hospitals and schools are still not made available by some governments, although in the case of earthquake disasters, first responders should be informed about their conditions. (2) News media and governments still do not pay attention to the quantitative estimates of fatalities 26 min (median) after earthquakes by QLARM and instead disseminate underestimates by up to two orders of magnitude for days and weeks. (3) The directions and extents of ruptures remain unknown for days and weeks, leading to poor information on the spatial distribution of victims at first. (4) Source locations by different worldwide and local agencies differ by several to 20 km, which can lead to misestimates of fatalities up to 20,000. If rapid earthquake locations of quality were available in earthquake prone areas, such errors could be avoided, and the time to estimate numbers of fatalities could be reduced by an order of magnitude.

Investigation of the radiosensitive properties of curcumin and temozolomide

Radiotherapy, one of the cancer treatment strategies, uses ionizing radiation to destroy cancer cells. It is very important to know the photon interaction parameters of curcumin, which has both anti-cancer and cancer-protective properties, to determine the penetration and energy accumulation in the interaction of radiation with tissue. In this work, the linear attenuation coefficient (LAC, μ), mass attenuation coefficient (MAC, μ/ρ), mean free path (MFP), half value layer (HVL), effective atomic number (Zeff), and electron density (Nel) of curcumin and temozolomide have been determined experimentally at 53.16 keV, 80.99 keV, 276.39 keV, 302.85 keV, 356.61 keV and 383.84 keV photon energies emitted from Ba133 point source by using the ULEGe detector. Besides, the radiation interaction parameters were calculated theoretically using the EpiXS software program. Also, the exposure buildup factors (EBF and EABF) of these compounds were determined up to 40 mfp in the energy range 0.015–15 MeV. The experimental and theoretical mass attenuation coefficients have been found to agree. The gamma-ray absorption efficiency of curcumin is approximately 3.89% higher than that of temozolomide. Temozolomide has approximately 25.6% higher fast neutron removal cross-section than curcumin.

Imaging microearthquake rupture processes using a dense array in Oklahoma

Both large and small earthquakes rupture in complex ways. However, microearthquakes are often simplified as point sources and their rupture properties are challenging to resolve. We leverage seismic wavefields recorded by a dense array in Oklahoma to image microearthquake rupture processes. We construct machine-learning enabled catalogs and identify four spatially disconnected seismic clusters. These clusters likely delineate near-vertical strike-slip faults. We develop a new approach to use the maximum absolute SH-wave amplitude distributions (S-wave wavefields) to compare microearthquake rupture processes. We focus on one cluster with earthquakes located beneath the dense array and have a local magnitude range of -1.3 to 2.3. The S-wave wavefields of single earthquakes are generally coherent but differ slightly between the low-frequency (<12 Hz) and high-frequency (>12 Hz) bands. The S-wave wavefields are coherent between different earthquakes at low frequencies with average correlation coefficients greater than 0.95. However, the wavefield coherence decreases with increasing frequency for different earthquakes. This reduced coherence is likely due to the rupture differences among individual earthquakes. Our results suggest that earthquake slip of the microearthquakes dominates the radiated S-wave wavefields at higher frequencies. Our method suggests a new direction in resolving small earthquake source attributes using dense seismic arrays without assuming a rupture model.