摘要：
In this paper, we synthesized and characterized a di-tetradentate macrocyclic ligand as a novel resonance fluorescence probe for the determination of uranium. The ligand contains two tetradentate ligand moieties and can chelate two cations to form binuclear complex. We found that when the ligand only chelates a uranyl ion or europium (III) ion, the formed complex can only produce weak resonance fluorescence. When the ligand chelates simultaneously uranyl and europium (III) to form heterobinuclear complex, the formed complex can produce strong resonance fluorescence due to the cation-cation interaction between uranyl and europium (III). Based on this finding, we established a resonance fluorescence chemosensor for the determination of uranium (VI) by utilizing the formation of the heterobinuclear complex. Under optimal conditions, the linear range for the determination of uranium (VI) is 0.008-1.2 nmol mL(-1) with a detection limit of 0.002 nmol mL(-1). The method has been applied to determine uranium (VI) in environmental water samples with the recoveries between 95.7% and 103.6%. (C) 2018 Elsevier B.V. All rights reserved.
摘要：
Oceanic subduction zones are important channels for carbon exchange between the Earth's crust and mantle. However, the nature of carbon cycles at depths from 120 to 410 km in the subduction zone remains unknown. To decipher this issue, high-precision stable Mg isotopes of arc-like volcanic rocks from Tengchong, Southwestern China, have been investigated. The Tengchong volcanic rocks comprise basalts and andesites, with Mg0 content varying from 2.41 to 8.48 wt.%. Both the basalts and andesites exhibit homogeneous and light Mg isotopic compositions with delta Mg-26 ranging from -0.51 to -0.45 parts per thousand and -0.49 to -0.33 parts per thousand, respectively. Their delta Mg-26 values are lower than the average mantle (delta Mg-26 = -0.25 +/- 0.07 parts per thousand) and island arc lavas (delta Mg-26 = -0.35 to +0.06%e), but similar to the <110 Ma intra-continental basalts from eastern China (delta Mg-26 = -0.60 to 0.30 parts per thousand). This light Mg isotopic composition could not originate from the accumulation of ilmenite in their mantle source because both the Nb/Ta and delta Mg-26 values of the basalts are invariant with TiO2 content. The recycling of carbonated eclogites is also unlikely because of the lack of any correlation between delta Mg-26 and either (Gd/Yb)(N) or Fe/Mn ratios in the Tengchong basalts. Alternatively, the most probable explanation for the light Mg isotopic composition is the recycling of sedimentary carbonates in the mantle source. This is supported by the high Na2O + K2O/TiO2 ratios (3.3-4.1), low Ti/Ti* and Hf/Hf* values in the basalts, which are consistent with the partial melting trend of carbonated peridotite. Additionally, the high Ba/Th, low Rb/Cs and enriched Sr-Nd isotopes (EMII-like endmember) of the Tengchong basalts indicate the presence of Indian sediments in their mantle source. Furthermore, the extremely high Th/U (6.5-8.3) ratios in basalts suggest the higher mobility of Th than U, which is a unique characteristic of slab-derived supercritical liquids in subduction zones with pressures greater than 6 GPa. Based on the quantitative modeling of Mg-Sr-Nd-Pb isotopes and trace elements, the mantle source of the Tengchong basalts lies along mixing lines of the DMM with 1% supercritical liquids and 15-19% recycled mixture containing 66-72% dolomite, 22-26% calcite and 2-12% Indian sediments. Given that the recycled mixture is mainly dolomite (66-72%), we proposed that the slab-derived supercritical liquids can dissolve dolomite and then metasomatized the overlying mantle to form carbonated peridotite. Partial melting of this mantle source should be located at a depth of similar to 120 to 300 km under which supercritical liquids can occur, which is supported by seismic tomographic observations. The Tengchong andesites display many geochemical features similar to the basalts, such as enrichments in LILEs (Large Ion Lithophile Elements), LREEs (Light Rare Earth Elements) and Sr-Nd-Pb isotopes, as well as low delta Mg-26 values, suggesting a petrogenetic link between these two rock types. Our detailed study suggests that the andesites evolved from the Tengchong basalts via assimilation and fractional crystallization (AFC) processes. This interpretation is also supported by the geophysical tomography, which reveals a low-velocity anomalous zone in the continental crust. This study reveals a new carbon cycle in which Mg-rich carbonate - dolomite - can be dissolved by supercritical liquids and subducted into a deep mantle wedge to depths of 120-300 km in the oceanic subduction zone. This deep metasomatic mantle wedge mixed with the upwelling mantle beneath the Tengchong volcano and partially melted to form the low delta Mg-26 volcanic rocks. (C) 2018 Elsevier Ltd. All rights reserved.
作者机构：
[Dai Bing] Univ South China, Nucl Resources Engn Coll, Hengyang 421001, Peoples R China.;[Zhao Guo-yan; Dai Bing] Cent S Univ, Sch Resources & Safety Engn, Changsha 410001, Hunan, Peoples R China.;[Konietzky, H.; Wasantha, P. L. P.; Dai Bing] TU Bergakad, Geotech Inst, D-09599 Freiberg, Germany.
通讯机构：
[Dai Bing] U;[Dai Bing] C;[Dai Bing] T;Univ South China, Nucl Resources Engn Coll, Hengyang 421001, Peoples R China.;Cent S Univ, Sch Resources & Safety Engn, Changsha 410001, Hunan, Peoples R China.
关键词：
damage evolution;loading and unloading;granitic rock;triaxial testing
摘要：
In-situ rock failures can result from stress changes due to pure loading and/or unloading. Understanding of the damage evolution behavior in brittle rocks during loading and unloading is imperative for the designs of rock structures. In this paper, we investigate the damage evolution characteristics of a granitic rock during loading and unloading after a series of triaxial experiments performed at different confining pressures. The axial stress-axial strain variations of the tested specimens revealed that the specimens undergoing unloading fail with a lower axial strain compared to the specimens failed purely by loading. Higher confining pressures were observed to exacerbate the difference. Volumetric strain versus axial strain curves indicated that the curves reverse the trend with the beginning of major damage of specimens. We suggest here a new form of equation to describe the secant modulus variation of brittle rocks against the axial stress for the unloading process. Failure mechanisms of tested specimens showed two distinct patterns, namely, specimens under pure loading failed with a single distinct shear fracture while for the unloading case specimens displayed multiple intersecting fractures. In addition, analysis of the evolution of dissipation and elastic energy during deformation of the specimens under loading and unloading conditions showed differentiable characteristics. Moreover, we evaluated the variations of two damage indices defined based on the energy dissipation and secant modulus evolution during deformation and observed that both of them satisfactorily distinguish key stages of damage evolution.
关键词：
Similarity model tests;Numerical simulation;Flow-aiding vibrator;Overhanging style;Field tests
摘要：
Arching, blocking, and sticking might be frequently encountered in hopper. Studies are carried out in order to solve these problems in Luoyang Bauxite Mine, China. The results of similarity model tests show that factors affecting flowability of particles are mainly friction and cohesion, when the moisture content changes from 82% to 10.8%, the influence of friction and cohesion on the flowability of particles becomes increasingly unfavorable, particles are easier to stay in the corners. In addition, the discharge effect is also affected by friction coefficient of the inner wall. In the numerical simulation, vibration is imposed by means of two blue balls fixed in the corners, where the flowability of particles is proved to be the worst. Results indicate that, no matter whether vibration is added or not, the total numbers of discharged particles and contacts change linearly with time steps, the contact forces between particles and walls are generally greater than that between particles. Compared with gravity discharge, the average velocities of the particles are obviously increased with the help of vibrations, especially in the corners of the hopper. The contact forces between particles as well as between particles and walls are optimized, that is, larger fluctuations of the contact forces are exhibited periodically, mainly because the contacts are greatly damaged by vibrations, therefore, the possibility of arching is limited effectively. The results of the studies reflect the mechanism of vibrations-aided gravitational flow and provide a theoretical basis for the design of a new vibrator. In combination with flow characteristics of particles, influencing factors of particle flow and theory of granular mechanics, a new flow-aiding vibrator with overhanging style in hopper is designed. In field tests, it has been proved to be a safe and effective device for solving problems of arching, blocking and sticking. (C) 2018 Elsevier B.V. All sights reserved.
摘要：
Radiation is a form of energy derived from a source that is propagated through material in space. It consists of ionizing radiation or nonionizing radiation. Ionizing radiation is a feature of the environment and an important tool in medical treatment, but it can cause serious damage to organisms. A number of protective measures and standards of protection have been proposed to protect against radiation. There is also a need for biomarkers to rapidly assess individual doses of radiation, which can not only estimate the dose of radiation but also determine its effects on health. Proteomics, genomics, metabolomics, and lipidomics have been widely used in the search for such biomarkers. These topics are discussed in depth in this review.
关键词：
triaxial test;loading and unloading;energy;damage degree;numerical simulation
摘要：
Theoretical and experimental studies have revealed that the damage evolution plays an important role in stability of rock structures. To investigate the damage characteristics of rocks during loading and unloading, a series of conventional triaxial tests and numerical simulations were conducted on granitic rock specimens under different confining pressures. The stress-strain characteristics and fracture patterns of tested specimens were first analyzed. It was found that the failure strain in unloading is smaller than the failure strain in loading. And the difference between the two strains is growing with increasing confining pressure. The failure patterns of specimens displayed two different failure mechanisms: a single distinct failure and a "X" failure. Based on the law of energy conservation, the energy evolution was analyzed. The results indicated that absorbed strain energy converted into elastic strain energy and dissipation energy. For evaluating and predicting damage, two damage degrees were proposed considering increase of dissipation energy and decrease of tangential modulus, respectively. The results show that before the reversal point of volumetric strain, the damage degrees were almost unchanged. During the process of unloading the damage degrees increases fast. For the same strain, lower confining pressure shows more damage. It indicates that the confining pressure has negative effects on increase of the damage degree. Then, the discrete element model based on elastic and unbreakable voronoi blocks was set-up for tri-axial tests. The energy evolution and damage process were simulated. And the ratio of failed contacts was used to simulate the damage degree. It shows that stress-strain behavior as well as micro- and macro-mechanical damage evolution can be reproduced by the DEM model.
摘要：
In this study, a novel magnetic core–dual shell Fe3O4@PDA@TiO2 adsorbents was successively prepared by polydopamine (PDA) coated and TiO2 film deposited on the surface of Fe3O4. The structure and properties were characterized by FT-IR, SEM–EDS TEM, VSM and XPS. The adsorption of U(VI) on Fe3O4@PDA@TiO2 was investigated as a function of contact time, solution pH, initial U(VI) concentration and other interfering ions. In addition, the U(VI) adsorption from practical wastewater and simulated seawater was also investigated. The results implied that the Fe3O4@PDA@TiO2 adsorbents exhibited promising adsorption performance for uranium (VI) from aqueous solution and simulated seawater.
作者机构：
[Xie, Shuibo; Gao, Xiang; Zeng, Taotao; Wang, Guohua; Zhang, Shiqi] Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reu, Hengyang, Peoples R China.;[Zeng, Taotao; Lens, Piet N. L.] UNESCO, IHE Inst Water Educ, Delft, Netherlands.;[Xie, Shuibo] Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Hengyang, Peoples R China.
通讯机构：
[Zeng, Taotao] U;Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reu, Hengyang, Peoples R China.;UNESCO, IHE Inst Water Educ, Delft, Netherlands.
关键词：
Uranium;Anaerobic granular sludge;Bacterial community composition;High-throughput sequencing
