The 6th Collaborative Materials Exercise, CMX-6, was organized by the Nuclear Forensic International Technical Working Group in 2018 and 2019. Two exercise samples, which had classical and nuclear ...forensic components, were distributed to nuclear forensic (NF) laboratories throughout the world. The goal of the exercise was to enable the NF laboratories to practice their capabilities under a realistic scenario, and share their experience in an open forum. Here we present the use of laser ablation triple quadrupole inductively coupled plasma mass spectrometry for the nuclear forensic examination of uranium and plutonium contaminated materials in CMX-6. Similarity or dissimilarity of exercise samples was established though trace element analysis and uranium and plutonium isotope ratio measurements.
We present a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method for trace-element analysis of uranium ore concentrates (UOCs). The method was used to characterize a select ...number of UOC samples representing 20 different producers from 8 distinct geographic locations. These results were then used to assess the origin of the samples using a machine-learning algorithm. The LA-ICP-MS characterization performed equally well as that obtained by the conventional aqueous method, suggesting that this rapid, low waste technique is suitable for National Nuclear Forensic Library applications.
A nuclear forensics investigation involving a uranium ore concentrate relies on accurate and precise analysis of impurities. Analytical data defensibility requires the use of reference materials as ...part of quality control. This study presents a compilation of trace element concentration results of the CUP-2 Uranium Ore Concentrate Standard measured by 11 different laboratories. The laboratories employed various dissolution methods, analytical preparation methods, and instrumental platforms. The data presented here contain concentrations of 66 impurities with up to 138 individual data points for each impurity. Consensus values have been assigned to each impurity following a statistical analysis of the data set.
Antioxidant mechanisms of curcumin, bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, have been studied by laser flash photolysis and pulse radiolysis. The keto−enol−enolate equilibrium of the ...heptadienone moiety of curcumin determines its physicochemical and antioxidant properties. In neutral and acidic aqueous solutions (from pH 3 to 7), the keto form dominates, and curcumin acts as an extraordinarily potent H-atom donor. The reaction rate constant with the methyl radical (3.5 ± 0.3) × 109 M-1 s-1 is close to diffusion control in 40% aqueous DMSO at pH 5. The tert-butoxyl radical reacts with curcumin in acetonitrile solutions at a diffusion controlled rate, k = (7.5 ± 0.8) × 109 M-1 s-1. The apparent site of reaction is the central CH2 group in the heptadienone link, which has two labile hydrogens. This is supported by comparing the reaction patterns of curcumin and dehydrozingerone (DHZ) (“half-curcumin”, 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one). DHZ does not react with the methyl radical, indicating that the presence of the labile hydrogens is crucial for the H-atom donating ability of curcumin. The tert-butoxyl radical reacts with DHZ at almost an order of magnitude lower rate (1.1 ± 0.1) × 109 M-1 s-1, clearly abstracting an H-atom from the phenolic OH group. The reaction mechanism of curcumin changes dramatically above pH 8, where the enolate form of the heptadienone link predominates. As a consequence, the reaction of the methyl radical diminishes completely in alkaline media, and the phenolic part of the molecule takes over as (electron donor) reaction site. The electron donating ability of curcumin is assessed from the measurements of one-electron-transfer equilibria of DHZ radicals. Reduction potential of the DHZ phenoxyl radical, E(pH = 6.5) = 0.83 ± 0.06 V, and E(pH = 13.0) = 0.47 ± 0.06 V vs NHE, which may be expected for an ortho-methoxy-substituted phenoxyl radical, indicate only moderate electron-donating ability. The importance of H-atom donation vs electron donation in free radical scavenging and antioxidant mechanisms of curcumin is discussed.
Open surgical aortic valve replacement (SAVR) is a viable alternative to transcatheter implantation in low-risk patients. In this light, we evaluated the safety and effectiveness of SAVR performed ...through conventional and less invasive surgical approaches in a high-volume center. We retrospectively reviewed the records of 395 consecutive patients who underwent open SAVR from January 2019 through December 2019 in our center. We evaluated and compared the operative results and postoperative major adverse outcomes of 3 surgical approaches: full median sternotomy (n=267), upper ministernotomy (ministernotomy) (n=106), and right anterior thoracotomy (minithoracotomy) (n=22). Overall, the 30-day all-cause mortality rate was 0.8% (3 patients). Stroke occurred in 8 patients (2%), disabling stroke in 4 patients (1%), myocardial infarction in 1 (0.2%), and surgical site infection in 13 (3.2%). There was no difference in 30-day mortality rate or incidence of postoperative major adverse events among the 3 surgical groups. Stroke and surgical site infection occurred more frequently, but not significantly so, in the full-sternotomy group. The mean hospital stay was longer after full sternotomy (9.1 ± 5.5 d) than after ministernotomy (7.5 ± 2.9 d) or minithoracotomy (7.4 ± 1.9 d) (P=0.012). Our findings suggest that open SAVR performed in a high-volume center is associated with a low early mortality rate and that less invasive approaches result in faster postoperative recovery and shorter hospital stays.
Adequate assessment of human health risk of uranium contamination at hazardous waste sites, which is an important step in determining the cleanup strategy, is based on bioavailability data. ...Bioavailability of uranium from contaminated soil has not been properly determined yet. Bioaccessibility is an in vitro conservative estimate of bioavailability and is thus frequently used for site-specific risk assessment. Bioaccessibility of uranium was measured in 33 soil samples from the Port Hope area in Ontario, Canada, by the physiologically based extraction test (PBET). Higher bioaccessibility values in the gastric plus intestinal phase, 48.4% ± 16.8%, than in the gastric phase, 20.8% ± 11.7%, are very probably the result of more efficient extraction of uranium from soil by intestinal fluid rich in carbonate ions. The observed variability of measured bioaccessibility values is discussed in light of the results of scanning electron microscope examination of the soil samples. Uranium bioaccessibility values in both gastric (acidic) and gastric plus intestinal (neutral) phases are higher in soil samples with smaller uranium-bearing particles and lower in samples where the uranium-bearing particles are larger. We postulate that the most important reason for variability of measured bioaccessibility values in Port Hope soil samples may be the difference in particle size of uranium-bearing particles.
In 2017, the Nuclear Forensics International Technical Working Group organized their fifth Collaborative Materials Exercise (CMX-5). The exercise samples were two uranium dioxide fuel pellets ...manufactured from the same starting materials by different processes to have similar bulk isotopic composition, but different spatial uranium isotopic distributions. Sets of identical materials were sent to all participating laboratories, who then utilized their existing nuclear forensic capabilities to independently analyse fuel pellets and identify similarities and differences of the materials’ characteristics. Here we present and compare the ability of different analytical techniques to spatially resolve uranium isotopic heterogeneity in the uranium oxide fuel pellets.
There is convincing epidemiological and in vitro evidence of chronic oxidative stress in individuals with Down syndrome (DS). These individuals develop Alzheimer like changes in the brain in their ...30s and 40s. The incidence of autoimmune diseases and cataracts is significantly increased, and the overall ageing process is accelerated. In vitro studies show that impaired viability of DS neurons may be amended by simple chemical antioxidants, such as vitamin E, BHT and propyl gallate, clearly indicative of oxyl radical involvement. However, because of the lack of in vivo experiments, the role of oxidative stress in DS remains controversial. We report here on the results of the chemical analyses of urine samples of 166 individuals, where DS subjects were matched by their siblings. The levels of 8-hydroxy-2′-deoxyguanosine (2.35 ± 1.69 in DS vs. 1.35 ± 1.04 in controls,
P = 0.00011), a biomarker of oxidative damage to DNA, and malondialdehyde (0.255 ± 0.158 in DS vs. 0.204 ± 0.128 in controls,
P = 0.033), a biomarker of lipid peroxidation, are significantly elevated in individuals with DS. Dietary influences failed to show any significant correlation with the oxidative stress biomarkers. These results provide direct evidence for increased oxidative stress in individuals with DS.
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