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[en] A sponge rubber nanocomposite based on styrene–butadiene rubber (SBR)/nanoclay (montmorillonite, MMT) or nano-calcium carbonate (CaCO) fillers with various foaming agent contents was produced by a simple technique, roll milling. The nanoparticles were examined by different techniques, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and Fourier-transform infrared (FT–IR). The sponge rubber nanocomposites were characterized by scanning electron microscopy (SEM) image analysis before and after exposures to radiation doses, as well as by the XRD patterns for the unirradiated samples. The different properties of the obtained nanocomposites, including their foaming degree, tensile strength, elongation at break, and thermal conductivity, were also investigated. The foam composites containing nano-CaCO possessed the best cell and crosslinking densities and mechanical properties among the other composites, while its foaming degree was the lowest. The results indicated that the thermal conductivity was reduced by increasing the foaming agent concentration. However, it increased as the radiation dose increased, and the optimum radiation dose was obtained at 75 kGy. The foam containing MMT exhibited an intermediate behavior while high thermal conductivity was recorded for the foam containing the CaCO nanoparticles.
[en] Non-Aqueous Phase Liquids (NAPLs) compounds are complex mixtures of organic liquids derived from petroleum or other industrial activities. Contamination of soils and groundwater by NAPLs can generate health and economic problems by compromising water resources, restrict soil use, and cause damage to the public and private patrimony and the environment. In the last decades, there has been an increase in areas contaminated by different types of NAPLs, a cause of great concern worldwide, mainly due to the difficulty of locating and quantifying contamination. These issues are majors obstacles that prevent the cleaning of soils and groundwater in affected locations. This work aims to use the concentrations of the Radon gas in the soil to identify areas contaminated by NAPL. The high affinity of the Radon for NAPLs causes a Radon deficit in soil gas in relation to the background observed in the studied region. After understanding the Radon affinity between soil gas, groundwater and NAPLs, a known contaminated area with diesel oil from a gas station spill was chosen to validate the methodology. Measurements of the Radon concentration were carried out with the AlphaGUARD® Radon monitor. These measurements confirmed the deficit in Radon concentration, which demonstrated the ability of this radionuclide to be used as a tracer for NAPL contamination, contributing to plans for remediation and control of pollution, as well as studies of oil wells on-shore. (author)
[en] The influence of N concentration on the crystallization kinetics, microstructural evolution, and composition of Ge-rich GeSbTe (GGST) alloys during thermal annealing, using X-ray diffraction and scanning and transmission electron microscopy is reported. It is shown that the incorporation of N in GGST tends to slow down the phase separation, crystallization, and growth processes during annealing. This can be attributed to the reduced diffusivity of Ge, which interacts and quickly bonds with N. Technological advantages of N doping are also discussed, considering the increased stability of the amorphous phase with respect to its parent crystalline phase, finer microstructure, flatness of the GeSbTe (GST) films after crystallization, and disappearance of the low-resistivity hexagonal phase at high temperature. (© 2020 Wiley‐VCH GmbH)
[en] The inflow of Atlantic Water to the Arctic Ocean is a crucial determinant for the future trajectory of this ocean basin with regard to warming, loss of sea ice, and ocean acidification. Yet many details of the fate and circulation of these waters within the Arctic remain unclear. Here, we use the two long-lived anthropogenic radionuclides I and U together with two age models to constrain the pathways and circulation times of Atlantic Water in the surface (10– 35 m depth) and in the mid-depth Atlantic layer (250–800m depth). We thereby benefit from the unique time-dependent tagging of Atlantic Water by these two isotopes. In the surface layer, a binary mixing model yields tracer ages of Atlantic Water between 9–16 years in the Amundsen Basin, 12–17 years in the Fram Strait (East Greenland Current), and up to 20 years in the Canada Basin, reflecting the pathways of Atlantic Water through the Arctic and their exiting through the Fram Strait. In the mid-depth Atlantic layer (250–800 m), the transit time distribution (TTD) model yields mean ages in the central Arctic ranging between 15 and 55 years, while the mode ages representing the most probable ages of the TTD range between 3 and 30 years. The estimated mean ages are overall in good agreement with previous studies using artificial radionuclides or ventilation tracers. Although we find the overall flow to be dominated by advection, the shift in the mode age towards a younger age compared to the mean age also reflects the presence of a substantial amount of lateral mixing. For applications interested in how fast signals are transported into the Arctic’s interior, the mode age appears to be a suitable measure. The short mode ages obtained in this study suggest that changes in the properties of Atlantic Water will quickly spread through the Arctic Ocean and can lead to relatively rapid changes throughout the upper water column in future years.
[en] This article presents nuclide-specific organ dose rate coefficients for environmental external exposures due to soil contamination assumed as a planar source at a depth of 0.5 g cm in the soil and submersion to contaminated air, for a pregnant female and its fetus at the 24th week of gestation. Furthermore, air kerma free-in-air coefficient rates are listed. The coefficients relate the organ equivalent dose rates (Sv s) to the activity concentration of environmental sources, in Bq m or Bq m, allowing to time-integrate over a particular exposure period. The environmental radiation fields were simulated with the Monte Carlo radiation transport codes PHITS and YURI. Monoenergetic organ dose rate coefficients were calculated employing the Monte Carlo code EGSnrc simulating the photon transport in the voxel phantom of a pregnant female and fetus. Photons of initial energies of 0.015–10 MeV were considered including bremsstrahlung. By folding the monoenergetic dose coefficients with the nuclide decay data, nuclide-specific organ doses were obtained. The results of this work can be employed for estimating the doses from external exposures to pregnant women and their fetus, until more precise data are available which include coefficients obtained for phantoms at different stages of pregnancy.
[en] The Cumulative Hazard Index method has been proposed for the first time to determine the low and high-risk levels of radionuclides. The significant radiological parameters and risk analyses for 226Ra, 232Th and 40K pollution levels control in the soil are determined through the probability distribution functions. The activity concentration of 226Ra, 232Th and 40K in samples were found to vary from of 16 ± 0.6 to 62 ± 3.2 Bq kg-1 with an average 30 ± 1.1 Bq kg-1, 24 ± 0.9 to 63 ± 1.3 Bq kg-1 with an average 37 ± 1.0 Bq kg-1 and 316 ± 5.8 to 878 ± 6.9 Bq kg-1 with an average 525 ± 6.2 Bq kg-1, respectively. (author)
[en] The present study attempts to provide a proper explanation to define the monazite source region and reason for its enrichment in coastal belts of Kollam district, Kerala. As part of that, primary data on enrichment of naturally occurring radionuclides viz. 40K, 226Ra, and 232Th in sand samples were collected from the study area and has been measured using NaI(Tl) detector. The radiological parameters were also calculated and compared with the Indian and World average values suggested by the UNSCEAR. The local variations in enrichment then connected with local lithology, drainage and sea wave direction for understanding the source and path of distribution. Connecting the dynamics of radioactivity concentration in a Geospatial study had finally provided details on source and locations of the parent material. (author)
[en] Black titanium dioxide (TiO) quantum dots (QDs) are grown by a solution-based electrochemical process and an effect of KCl concentration on the growth is investigated. The electrochemical process is demonstrated as a simple one-step process for the growth of black TiO QDs in the solutions via bottom-up process. From the absorption spectra, the absorption appears for an entire visible wavelength (400-700 nm) implying a black TiO property. The average size of the black TiO QDs is about 4.5 nm from the transmission electron microscopy results and is similar to all KCl concentrations. This indicates that KCl concentration has no effect on the particle size, but has effect on the hydrodynamic size of TiO QDs. The black TiO QDs can be produced by the hydrogenation process of hydrogen ions during electrochemical process. The obtained black TiO QDs can be further explored as an electron-transporting layer for a perovskite solar cell application. (© 2020 Wiley‐VCH GmbH)
[en] The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture launched a new Coordinated Research Project (D1.50.19) called “Monitoring and Predicting Radionuclide Uptake and Dynamics for Optimizing Remediation of Radioactive Contamination in Agriculture'', in October 2019. Within the CRP, the high-throughput characterization of soil properties and the estimation of soil-to-plant transfer factors of radionuclides are of critical importance. As already highlighted in Soils Newsletter Vol. 43, No. 1, July 2020, for several decades, soil researchers have been successfully using near and mid-infrared spectroscopy (MIRS) techniques to estimate a wide range of soil properties (Carbon, Nitrogen, CEC, Clay, Sand, pH, ...). In recent years, soil science researchers are increasingly shifting their focus from traditional modeling techniques such as PLSR (Partial Least Squares Regression) to new classes of algorithms, such as Ensemble Learning (Random Forest, Boosting, …) or Deep Learning (Convolutional Neural Networks), that have proven to outperform PLSR on most (if not all) soil properties prediction in a large data regime.
[en] Under the CRP D1.50.19 focusing on the optimization of remediation of radioactive contaminated agricultural land, one important objective is to update the existing decision support system DSS4NAFA to support data management during remediation activities in the aftermath of a nuclear emergency affecting food and agriculture. During remediation, the need exists for keeping an overview of the remediation activities and, in particular, where, when and how these activities are carried out. Further, it is imperative to keep track of the efficiency and effectiveness of remediation activities (e.g. reduction of soil and food contamination). At this moment the workflow for the remediation module is being developed in close collaboration with the CRP D1.50.19 research partners from across the world for addressing the above-mentioned needs for enhanced data management during remediation.