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Jana Timkova, Lukas Kotik, Ladislav Tomasek
This paper assesses the coverage probability of commonly used confidence intervals for the standardized mortality ratio (SMR) when death certificates are missing. It also proposes alternative confidence interval approaches with coverage probabilities close to .95. In epidemiology, the SMR is an important measure of risk of disease mortality (or incidence) to compare a specific group to a reference population. The appropriate confidence interval for the SMR is crucial, especially when the SMR is close to 1.0 and the statistical significance of the risk needs to be determined...
August 16, 2017: Statistics in Medicine
Richard N Collins, Kevin M Rosso
Molecular-level pathways in the aqueous redox transformation of uranium by iron remain unclear, despite the importance of this knowledge for predicting uranium transport and distribution in natural and engineered environments. As the relative importance of homogeneous versus heterogeneous pathways is difficult to probe experimentally, here we apply computational molecular simulation to isolate rates of key one electron transfer reactions in the homogenous pathway. By comparison to experimental observations the role of the heterogeneous pathway also becomes clear...
August 15, 2017: Journal of Physical Chemistry. A
Sebastian Schöne, Thomas Radoske, Juliane März, Thorsten Stumpf, Michael Patzschke, Atsushi Ikeda-Ohno
A simple synthesis based on UO2Cl2·n(H2O) and 1,10-phenanthroline (phen) resulted in the formation of a new uranyl(VI) complex [UO2Cl2(phen)2] (1), revealing a unique dodecadeltahedron coordination geometry around the uranium centre with significant bending of the robust linear arrangement of the uranyl (O─U─O) unit. Quantum chemical calculations on complex 1 indicated that the weak but distinct interactions between the uranyl oxygens and the adjacent hydrogens of phen molecules play an important role in forming the dodecadeltahedron geometry that fits to the crystal structure of 1, resulting in the bending the uranyl unit...
August 14, 2017: Chemistry: a European Journal
C A Stitt, C Paraskevoulakos, A Banos, N J Harker, K R Hallam, A Davenport, S Street, T B Scott
Uranium encapsulated in grout was exposed to water vapour for extended periods of time. Through synchrotron x-ray powder diffraction and tomography measurements, uranium dioxide was determined the dominant corrosion product over a 50-week time period. The oxide growth rate initiated rapidly, with rates comparable to the U + H2O reaction. Over time, the reaction rate decreased and eventually plateaued to a rate similar to the U + H2O + O2 reaction. This behaviour was not attributed to oxygen ingress, but instead the decreasing permeability of the grout, limiting oxidising species access to the metal surface...
August 11, 2017: Scientific Reports
Michael C Hamel, J Kyle Polack, Marc L Ruch, Matthew J Marcath, Shaun D Clarke, Sara A Pozzi
The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation...
August 11, 2017: Scientific Reports
K A Erickson, B D Kagan, B L Scott, D E Morris, J L Kiplinger
The reaction of (C5Me5)2AnCl2 (An = Th, U) with 2.8 or 4 equivalents of LiNMe2, respectively, affords (C5Me5)2An(NMe2)2 in high yields. In addition to improved syntheses, the solid-state structures, voltammetric data, and UV-visible-NIR spectra for these classic actinide bis(dimethylamido) complexes are presented for the first time.
August 10, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Geng Bang Jin, Christos D Malliakas, Jian Lin
To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP2, β-ThCu2P2, and ThCu5P3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP2 can be described as a filled UTe2-type with both dimeric P2(4-) and monomeric P(3-) anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu2P2 contains only P(3-) anions and is isostructural with BaCu2S2...
August 10, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
K E Westaway, J Louys, R Due Awe, M J Morwood, G J Price, J-X Zhao, M Aubert, R Joannes-Boyau, T M Smith, M M Skinner, T Compton, R M Bailey, G D van den Bergh, J de Vos, A W G Pike, C Stringer, E W Saptomo, Y Rizal, J Zaim, W D Santoso, A Trihascaryo, L Kinsley, B Sulistyanto
Genetic evidence for anatomically modern humans (AMH) out of Africa before 75 thousand years ago (ka) and in island southeast Asia (ISEA) before 60 ka (93-61 ka) predates accepted archaeological records of occupation in the region. Claims that AMH arrived in ISEA before 60 ka (ref. 4) have been supported only by equivocal or non-skeletal evidence. AMH evidence from this period is rare and lacks robust chronologies owing to a lack of direct dating applications, poor preservation and/or excavation strategies and questionable taxonomic identifications...
August 9, 2017: Nature
Lukas Nejdl, Jindrich Kynicky, Martin Brtnicky, Marketa Vaculovicova, Vojtech Adam
Toxic metal contamination of the environment is a global issue. In this paper, we present a low-cost and rapid production of amalgam electrodes used for determination of Cd(II) and Pb(II) in environmental samples (soils and wastewaters) by on-site analysis using difference pulse voltammetry. Changes in the electrochemical signals were recorded with a miniaturized potentiostat (width: 80 mm, depth: 54 mm, height: 23 mm) and a portable computer. The limit of detection (LOD) was calculated for the geometric surface of the working electrode 15 mm² that can be varied as required for analysis...
August 9, 2017: Sensors
Xiaoqing Gao, Mingliang Bi, Keliang Shi, Zhifang Chai, Wangsuo Wu
The effect of pH, contact time, temperature, ionic strength and initial U(VI) concentration on U(VI) sorption onto K-feldspar was investigated using batch techniques. The sorption kinetics was evaluated and the activation energy was obtained based on the rate constants at different temperature. Graphical correlations of sorption isotherm models have been evaluated and applied for U(VI) uptake by K-feldspar. Various thermodynamic parameters, such as, Gibb's free energy, entropy and enthalpy of the on-going sorption process have been calculated and the possible sorption mechanism of U(VI) was deduced...
July 25, 2017: Applied Radiation and Isotopes
Mateusz Dembowski, Christopher A Colla, Ping Yu, Jie Qiu, Jennifer E S Szymanowski, William H Casey, Peter C Burns
Understanding the stability fields and decomposition products of various metal- and actinide-oxide nanoclusters is essential for their development into useful materials for industrial processes. Herein, we explore the spontaneous transformation of the sulfate-centered, phosphate functionalized uranyl peroxide nanocluster {U20P6} to {U24} under aqueous ambient conditions using time-resolved small-angle X-ray scattering, Raman, and (31)P NMR spectroscopy. We show that the unusual μ-η(1):η(2) bridging mode of peroxide between uranyl ions observed in {U20P6} may lead to its rapid breakdown in solution as evidenced by liberation of phosphate groups that were originally present as an integral part of its cage structure...
August 7, 2017: Inorganic Chemistry
Sen Yang, Jun Qian, Liangju Kuang, Daoben Hua
It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands...
August 17, 2017: ACS Applied Materials & Interfaces
Chad Priest, Bo Li, De-En Jiang
Exploring the structural interplay of ligands with uranyl can provide important knowledge for technology advances in uranium extraction from seawater. However, obtaining such chemical information is not an easy endeavor experimentally. From a plethora of computational methods, this work provides both microscopic insights and free-energy profiles of the binding between uranyl and deprotonated glutardiamidoxime (H2B) for which experimental structural information is not available, despite H2B being an important model ligand with an open-chain conformation for understanding aqueous uranium extraction chemistry...
August 7, 2017: Inorganic Chemistry
J M Zhan, X Yang, W M Zhou
No abstract text is available yet for this article.
June 20, 2017: Chinese Journal of Industrial Hygiene and Occupational Diseases
Ekaterina M Dutova, Aleksei N Nikitenkov, Vitaly D Pokrovskiy, David Banks, Bjørn S Frengstad, Valerii P Parnachev
Generic hydrochemical modelling of a grantoid-groundwater system, using the Russian software "HydroGeo", has been carried out with an emphasis on simulating the accumulation of uranium in the aqueous phase. The baseline model run simulates shallow granitoid aquifers (U content 5 ppm) under conditions broadly representative of southern Norway and southwestern Siberia: i.e. temperature 10 °C, equilibrated with a soil gas partial CO2 pressure (PCO2, open system) of 10(-2.5) atm. and a mildly oxidising redox environment (Eh = +50 mV)...
August 3, 2017: Journal of Environmental Radioactivity
Carlos A Jerez
Mining activities have been carried out for thousands of years and nowadays have an enormous worldwide use to obtain important metals of industrial use. These include copper, iron, gold and several others. Although modern mining companies have sustainable mining programs that include tailings management and external verifications, it is recognized that these industrial activities are responsible for a significant damage to the environment. Specially, technologies such as smelting and roasting generate very toxic emissions, including solid particles in the air, very large tailings and contribute to generate acid mine drainage (AMD) that affects humans health and all kinds of living plants, animals and microorganisms...
August 3, 2017: Microbial Biotechnology
Fotini Noli, Panagiotis Tsamos
The radiological and chemical pollution of a cluster of four lakes in a lignite mining area of North-Western Greece was investigated using a variety of analytical techniques. Alpha spectrometry was applied to measure the activity concentrations of the uranium radioisotopes (U-234, U-235, and U-238) in waters. The mass activities of U-238, Th-232, and K-40 in sediments were measured by high-resolution gamma spectrometry. Furthermore, the determination of the minor and trace elements was carried out by instrumental neutron activation analysis (INAA) in both water and sediments samples, respectively...
August 3, 2017: Environmental Science and Pollution Research International
Fern Sinclair, Johann A Hlina, Jordann A L Wells, Michael P Shaver, Polly L Arnold
The C3-symmetric uranium(iv) and cerium(iv) complexes Me3SiOM(OAr(P))3, M = U (1), Ce (2), OAr(P) = OC6H2-6-(t)Bu-4-Me-2-PPh2, have been prepared and the difference between these 4f and 5f congeners as initiators for the ring opening polymerisation (ROP) of l-lactide is compared. The poorly controlled reactivity of the homoleptic analogue U(OAr(P))4 (3) demonstrates the importance of the M-OSiMe3 initiating group. The incorporation of a nickel atom in 1 to form the U-Ni heterobimetallic complex Me3SiOU(OAr(P))3Ni (4) may be the first example of the use of the inverse trans influence to switch the reactivity of a complex...
August 2, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
E M El Afifi, A M Shahr El-Din, R F Aglan, E H Borai, M M Abo-Aly
Egyptian monazite is a promising resource and investment attractive for production of valuable metals of industrial or nuclear interest such as rare earth elements (REEs), thorium (Th) and uranium (U). The study was focused to establish a baseline framework in viewpoint of radiation protection for the workers in production of REEs from high-grade monazite treated by sodium hydroxide (NaOH) solutions. Radiological hazard indices (cancer, gonadal and other risks) were evaluated, due to emissions (α-, β- and γ-radiations) of radium-isotopes ((228)Ra, (226)Ra, (223)Ra) and lead ((210)Pb)...
July 29, 2017: Regulatory Toxicology and Pharmacology: RTP
Jennifer N Wacker, Monica Vasiliu, Kevin Huang, Ryan E Baumbach, Jeffery A Bertke, David A Dixon, Karah E Knope
The room temperature synthesis and structural characterization of two U(IV) compounds isolated from acidic aqueous solution is reported. Evaporation of a U(IV)/HCl solution containing pyridinium (HPy) yielded (HPy)2UCl6 (1), yet in the presence of an organic carboxylate U(H2O)4Cl4·(HPy·Cl)2 (2) is obtained. The structures have been determined by single crystal X-ray diffraction and characterized by Raman, IR, and optical spectroscopies. The magnetism of both compounds was also investigated. The structure of 1 is built from UCl6(2-) anionic units, pervasive in descriptions of the aqueous chemistry of tetravalent uranium, and is found to undergo a phase transition from C2/m to P1̅ upon cooling...
July 31, 2017: Inorganic Chemistry
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