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Nicholas R Andreychuk, Tara Dickie, David J H Emslie, Hilary A Jenkins
Palladium-catalyzed coupling of 1-adamantylamine (2 equiv.) with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylxanthene afforded the proligand 4,5-bis(1-adamantylamino)-2,7-di-tert-butyl-9,9-dimethylxanthene, H2 [XAd] (1), which upon deprotonation with excess KH or KCH2 Ph in THF or dme generated [{K(THF)3 }2 (XAd)] (2a) and [K2 (XAd)(dme)] (2b). Subsequent reaction of in situ generated 2a or 2b with [ThCl4 (dme)2 ] yielded [(XAd)ThCl4 K2 ]·x(dme) (3; x = 0.5-2), which reacted with 2 equiv. of LiCH2 SiMe3 or K[allylTMS ] to afford the bis(hydrocarbyl) complexes [(XAd)Th(CH2 SiMe3 )2 (THF)] (4) and [(XAd)Th(η3 -allylTMS )2 ] {5; allylTMS = 1-(SiMe3 )C3 H4 }...
March 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
F Nestola, N Korolev, M Kopylova, N Rotiroti, D G Pearson, M G Pamato, M Alvaro, L Peruzzo, J J Gurney, A E Moore, J Davidson
Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth's mantle. Discoveries of some of these minerals in 'super-deep' diamonds-formed between two hundred and about one thousand kilometres into the lower mantle-have confirmed part of this picture. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3 ). This mineral-expected to be the fourth most abundant in the Earth-has not previously been found in nature...
March 7, 2018: Nature
M F S Casagrande, D M Bonotto
This paper describes an alternative method for evaluating gross alpha and beta radioactivity in waters by using γ-rays analysis performed with hyper-pure germanium detector (HPGe). Several gamma emissions related to α and β- decays were used to provide the activity concentration data due to natural radionuclides commonly present in waters like40 K and those belonging to the238 U and232 Th decay series. The most suitable gamma emissions related to β- decays were214 Bi (1120.29 keV,238 U series) and208 Tl (583...
February 23, 2018: Applied Radiation and Isotopes
Yaoyao Huang, Yang Hu, Lvcun Chen, Tao Yang, Hanfang Huang, Runping Shi, Peng Lu, Chenghua Zhong
Low-cost biosorbents (ginkgo leaf, osmanthus leaf, banyan leaf, magnolia leaf, holly leaf, walnut shell, and grapefruit peel) were evaluated in the simultaneous removal of La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Yb3+, Lu3+, UO22+, Th4+, Y3+, Co2+, Zn2+, Ni2+, and Sr2+ from aqueous solutions. In single metal systems, all adsorbents exhibited good to excellent adsorption capacities toward lanthanides and actinides. In a simulated multicomponent mixed solution study, higher selectivity and efficiency were observed for Th4+ over other metal cations, with ginkgo leaves providing the highest adsorptivity (81...
2018: PloS One
Giorgia Cinelli, Tore Tollefsen, Peter Bossew, Valeria Gruber, Konstantins Bogucarskis, Luca De Felice, Marc De Cort
The European Atlas of Natural Radiation is a collection of maps displaying the levels of natural radioactivity caused by different sources. It has been developed and is being maintained by the Joint Research Centre (JRC) of the European Commission, in line with its mission, based on the Euratom Treaty: to collect, validate and report information on radioactivity levels in the environment of the EU Member States. This work describes the first version of the European Atlas of Natural Radiation, available in digital format through a web portal, as well as the methodology and results for the maps already developed...
February 26, 2018: Journal of Environmental Radioactivity
Pei Zhao, Xiang Zhao, Masahiro Ehara
Th@C76 has been studied by density functional theory combined with statistical mechanics calculations. The results reveal that Th@Td (19151)-C76 satisfying the isolated pentagon rule possesses the lowest energy. Nevertheless, considering the enthalpy-entropy interplay, Th@C1 (17418)-C76 with one pair of adjacent pentagons is thermodynamically favorable at elevated temperatures, which is reported for the first time. The bonding critical points in both isomers were analyzed to disclose covalent interactions between the inner Th and cages...
February 26, 2018: Inorganic Chemistry
V Pereda-Loth, X Franceries, A S Afonso, A Ayala, B Eche, D Ginibrière, G Gauquelin-Koch, M Bardiès, L Lacoste-Collin, M Courtade-Saïdi
Astronauts are exposed to microgravity and chronic irradiation but experimental conditions combining these two factors are difficult to reproduce on earth. We have created an experimental device able to combine chronic irradiation and altered gravity that may be used for cell cultures or plant models in a ground based facility. Irradiation was provided by thorium nitrate powder, conditioned so as to constitute a sealed source that could be placed in an incubator. Cell plates or plant seedlings could be placed in direct contact with the source or at various distances above it...
February 2018: Life Sciences in Space Research
D L Hoffmann, C D Standish, M García-Diez, P B Pettitt, J A Milton, J Zilhão, J J Alcolea-González, P Cantalejo-Duarte, H Collado, R de Balbín, M Lorblanchet, J Ramos-Muñoz, G-Ch Weniger, A W G Pike
The extent and nature of symbolic behavior among Neandertals are obscure. Although evidence for Neandertal body ornamentation has been proposed, all cave painting has been attributed to modern humans. Here we present dating results for three sites in Spain that show that cave art emerged in Iberia substantially earlier than previously thought. Uranium-thorium (U-Th) dates on carbonate crusts overlying paintings provide minimum ages for a red linear motif in La Pasiega (Cantabria), a hand stencil in Maltravieso (Extremadura), and red-painted speleothems in Ardales (Andalucía)...
February 23, 2018: Science
Cassia F Read, David H Duncan, Chiu Yee Catherine Ho, Matt White, Peter A Vesk
Plant ecologists require spatial information on functional soil properties but are often faced with soil classifications that are not directly interpretable or useful for statistical models. Sand and clay content are important soil properties because they indicate soil water-holding capacity and nutrient content, yet these data are not available for much of the landscape. Remotely sensed soil radiometric data offer promise for developing statistical models of functional soil properties applicable over large areas...
February 2018: Ecology and Evolution
Anna Luiza Marques Ayres da Silva, Sérgio Médici Eston, Wilson Siguemasa Iramina, Diego Diegues Francisca
Radon is a chemically inert noble radioactive gas found in several radioactive decay chains. In underground mines, especially those that contain or have contained ores associated with uranium-bearing minerals, workers might be exposed to high levels of radon and its decay products (RDP). This work aimed to investigate whether the exposure of workers to radon gas and its progeny has been evaluated in Brazilian non-uranium and non-thorium underground mines. If so, the results and control measures undertaken or recommended to maintain the concentrations under Brazilian occupational exposure limits (OELs) were documented...
February 14, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
Mumei Chen, Zheng Li, Yiyun Geng, Haogui Zhao, Shuhua He, Qingnuan Li, Lan Zhang
As a kind of three-dimensional graphene architecture material with superhydrophobic, low density, high specific surface area and porosity, graphene aerogel (GA) can be used to immobilize extractant to constitute the solvent impregnated adsorbent. In this paper, the N,N,N',N'-tetraoctyldiglycolamide impregnated graphene aerogel ( GA-TODGA) was prepared to remove the thorium from aqueous solution. It is found that the adsorption of thorium on GA-TODGA is strongly dependent on the concentration of TODGA in GA and HNO3 in aqueous solution...
May 1, 2018: Talanta
S M Pérez-Moreno, M J Gázquez, R Pérez-López, J P Bolivar
Determining the availability of natural radionuclides in environmental conditions is increasingly important in order to evaluate their toxicity. A validated procedure is necessary to ensure the comparability and accuracy of the results obtained by different laboratories. For that, an optimised BCR sequential extraction procedure has been applied to the certified reference material (CRM), coded as BCR-701, and their resulting liquid and solid fractions were subjected to an exhaustive chemical and radioactivity characterisation...
February 1, 2018: Chemosphere
Romilton Dos Santos Amaral, Elaíze Nídia de Lima Morais, José Araújo Dos Santos Júnior, Arykerne Nascimento Casado da Silva, Jairo Dias Bezerra, Otávio Pereira Dos Santos Junior
A marine phosphorus region with high concentrations of phosphate, coastwise of Pernambuco, Northeast of Brazil, is densely inhabited. Rock phosphate deposits naturally contain uranium ore that produces ionizing radiation from it and its natural descendants, furthermore, its thorium and potassium concentrations are comparable to those usually found in soils. Radiological monitoring of this environment is important to verify the occurrence of harmful effective doses for the adjacent population. This study aimed at the in situ radiometric monitoring in four cities of the north of the Metropolitan Region of Recife-Pernambuco, estimating the effective environmental dose to which the local population is subject...
February 3, 2018: Radiation Protection Dosimetry
Giorgia Cinelli, Francois Tondeur, Boris Dehandschutter
The European Atlas of Natural Radiation developed by the Joint Research Centre (JRC) of the European Commission includes maps of potassium K and thorium Th. With several different databases available, including data (albeit not calibrated) from an airborne survey, Belgium is a favourable case for exploring the methodology of mapping for these natural radionuclides. Harmonized databases of potassium and thorium in soil were built by radiological (not airborne) and geochemical data. Using this harmonized database it was possible to calibrate the data from the airborne survey...
February 2, 2018: Journal of Environmental Radioactivity
Yaxing Wang, Huangjie Lu, Xing Dai, Tao Duan, Xiaojing Bai, Yawen Cai, Xuemiao Yin, Lanhua Chen, Juan Diwu, Shiyu Du, Ruhong Zhou, Zhifang Chai, Thomas E Albrecht-Schmitt, Ning Liu, Shuao Wang
The coexistence of radioactive contaminants (e.g., thorium, uranium, and their daughters) in rare earth minerals introduces significant environmental, economic, and technological hurdles in modern rare earth production. Efficient, low cost, and green decontamination strategies are therefore desired to ameliorate this problem. We report here a single-step and quantitative decontamination strategy of thorium from rare earths based on a unique periodic trend in the formation of crystalline selenite compounds across the lanthanide series, where Ce(III) is fully oxidized in situ to Ce(IV)...
February 2, 2018: Inorganic Chemistry
Meiying Qie, Jian Lin, Fang Kong, Mark A Silver, Zenghui Yue, Xiaomei Wang, Linjuan Zhang, Hongliang Bao, Thomas E Albrecht-Schmitt, Jian-Qiang Wang
The exploration of phase formation in the f-element-bearing iodate selenate system has resulted in 14 novel rare-earth-containing iodate selenates, Ln(IO3)(SeO4) (Ln = La, Ce, Pr, Nd; LnISeO-1), Ln(IO3)(SeO4)(H2O) (Ln = Sm, Eu; LnISeO-2), and Ln(IO3)(SeO4)(H2O)2·H2O (Ln = Gd, Dy, Ho, Er, Tm, Yb, Lu, Y; LnISeO-3), as well as two new thorium iodate selenates, Th(OH)(IO3)(SeO4)(H2O) (ThISeO-1) and Th(IO3)2(SeO4) (ThISeO-2). LnISeO-3 and ThISeO-2 crystallize in the chiral space group P212121, while LnISeO-1, LnISeO-2, and ThISeO-1 crystallize in the centrosymmetric space group P21/c...
January 18, 2018: Inorganic Chemistry
Neta Arad-Vosk, Rotem Beach, Amichai Ron, Tzvi Tzvi Templeman, Yuval Golan, Gabby Sarusi, Amir Sa'ar
Thin films of lead sulfide alloyed with thorium and oxygen were deposited on GaAs substrates and processed to produce a photo-diode structure. Structural, optical and electrical characterizations indicate the presence of small nanoscale domains that are characterized by dense packaging, high quality interfaces and a blue-shift of the energy bandgap toward the short wavelength infrared range of the spectrum. Photocurrent spectroscopy revealed a considerable photo-conductivity that is correlated with excitation of carriers in the nanoscale domains of lead sulfide alloyed with thorium and oxygen...
January 17, 2018: Nanotechnology
Zahra Safaei Moghaddam, Massoud Kaykhaii, Mostafa Khajeh, Ali Reza Oveisi
In this study, a zirconium-based metal-organic framework (Zr-MOF), named UiO-66-OH, was synthesized by the solvo-thermal method and characterized by Fourier transform-infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). This Zr-MOF was then employed as a sorbent for selective extraction and preconcentration of thorium ions after their complexation with 2‑(2,4‑dihydroxyphenyl)‑3,5,7‑trihydroxychromen‑4‑one (morin) from environmental water samples prior to its spectrophotometrical determination...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Isaac J Arnquist, Eric W Hoppe, Mary Bliss, Jay W Grate
No abstract text is available yet for this article.
January 3, 2018: Analytical Chemistry
Irena Wysocka, Emilia Vassileva
This article describes the development and validation of an analytical procedure for the matrix separation, preconcentration and determination of sub-ng kg-1 levels 232Th in a small volume (20 mL) of seawater samples. The matrix separation and Th preconcentration was carried out using a commercially available ion-chelation system seaFAST-pico. The acidified to pH < 2 seawater samples were mixed on-line with the ammonium acetate buffer (pH of 6.0 ± 0.2) before loading on the column containing resin with iminodiacetic and ethylenediaminetriacetic functional groups...
February 13, 2018: Analytica Chimica Acta
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