ALBERT

Description: Two different confinement transition discharges, the low-intermediate-high (L-I-H) and the low-intermediate-low (L-I-L) confinement transitions, respectively, have been obtained by lower hybrid current drive with lithium wall conditioning in the EAST superconducting tokamak. The dynamic features of short-scale turbulent fluctuations in the two discharges are investigated by a tangential CO 2 laser collective scattering system. It is found that the great changes of broadband fluctuations in amplitude and structure characteristics are closely related to the choice of the final transition to H-mode. These results could shed light on the understanding of the L-H transition mechanism.

Description: X-ray photoelectron spectroscopy (XPS) was utilized to measure the valence band offset (Δ E V ) of the TiZnSnO (TZTO)/Si heterojunction. TZTO films were deposited on Si (100) substrates using magnetron sputtering at room temperature. By using the Zn 2 p 3/2 and Sn 3 d 5/2 energy levels as references, the value of Δ E V was calculated to be 2.69 ± 0.1 eV. Combining with the experimental optical energy band gap of 3.98 eV for TZTO extracted from the UV-vis transmittance spectrum, the conduction band offset (Δ E C ) was deduced to be 0.17 ± 0.1 eV at the interface. Hence, the energy band alignment of the heterojunction was determined accurately, showing a type-I form. This will be beneficial for the design and application of TZTO/Si hybrid devices.

Description: The Handan-Xingtai district in the North China craton is one of the most important concentrations of iron skarn deposits in China, with proven reserves of 900 to 1,000 Mt at an average of 40 to 55 wt % Fe. The iron mineralization occurs predominantly along contact zones between Early Cretaceous intermediate-silicic intrusions and Middle Ordovician marine carbonates intercalated with numerous evaporite beds. In this paper, we present textural features and laser ablation ICP-MS U-Pb dating results of hydrothermal zircon from five major iron skarn deposits to place tight constraints on the timing and duration of the district-scale iron mineralization. Zircon grains from the mineralized skarns are anhedral to subhedral crystals and euhedral tetragonal bipyramids. They are closely intergrown or texturally associated with diopside, garnet, epidote, calcite, albite, and phlogopite. Other common minerals in the skarn assemblages include F-rich hornblende, wilkeite-F, F-apatite, and fluorite. Zircon grains typically contain abundant inclusions of skarn minerals and daughter mineral-rich (mostly magnetite, halite, and sylvite) fluid inclusions. Compositionally, these zircon grains have moderately to extremely high Th (518–7,477 ppm) and U (109–25,610 ppm) contents, with highly variable Th/U ratios ranging from 0.01 to 5.23. The morphological, textural, and geochemical features of the zircons confirm their hydrothermal origin and indicate that they most likely precipitated from high-temperature, F-rich, magmatic-derived ore-forming fluids. The hydrothermal zircon grains yield well-defined concordant U-Pb ages for the five studied iron skarn deposits, with weighted mean 206 Pb/ 238 U dates ranging from 133.6 ± 0.9 to 128.5 ± 1.4 Ma (2 ). These ages are remarkably consistent with U-Pb ages (134.1 ± 1.2 to 128.5 ± 0.9 Ma; 2 ) of magmatic zircon grains from the ore-related intrusions in each deposit, demonstrating that iron skarn mineralization was genetically related to the coeval magmatism. Our new geochronological data, when combined with existing isotopic ages, indicate that iron mineralization and associated magmatism in the Handan-Xingtai district took place mainly at the ca. 137–133 and 131–128 Ma intervals. Iron skarn deposits of similar ages also occur widely in other parts of the eastern North China craton, forming the only known giant Mesozoic iron skarn province in a cratonic block on the Earth. The formation of these iron skarn deposits and associated intrusions coincided in time with lithospheric thinning or destruction of the North China craton, strongly suggesting a causal link between the two processes.

Description: The transition-metal dichalcogenides provided a good platform for the investigation of superconductivity and charge-density-wave (CDW) order. A series of high quality 6 R -TaS 2− x Se x (0 ≤  x  ≤ 1.6) single crystals were fabricated by the chemical-vapor-transport method and systematically investigated. The CDW becomes more stable with more S being replaced by Se, which causes expansion of the lattice, and produces a negative chemical pressure in the system. The x dependence of the onset of superconductivity ( T c onset ) shows a dome-like shape with a maximum of T c onset  = 2.7 K at x  = 0.8. The magnetic susceptibility (4π χ ) of x  = 0.8 under the hydrostatic pressure P  = 1.0 GPa was also measured, which showed a small increase of T c and superconducting volume fraction. A pronounced peak effect was observed in the isothermal hysteresis with magnetic field ( H ) parallel to c -axis, which may arise from the quenching inhomogeneity and/or the stacking disorder. Finally, the evolution of the electronic states tuned by Se-doping was summarized in the phase diagram.

Description: This paper aims to develop three-dimensional fundamental thermo-elastic solutions for an infinite/half-infinite space of a two-dimensional hexagonal quasi-crystal, which is subjected to a point heat source. Starting from the newly developed general solution in terms of quasi-harmonic potential functions, the corresponding fundamental solutions are derived by means of the trial-and-error technique. Six appropriate potential functions involved in the general solution are observed. The present fundamental solutions are applied to construct boundary integral equations governing the contact problems. Numerical calculations are performed to show the distributions of the thermo-elastic coupling field variables in a half-space subjected to a point thermal source.

Description: The Kangdian iron oxide copper-gold (IOCG) metallogenic province contains a number of economically important Fe-Cu deposits in South China and northern Vietnam. Due to the lack of precise mineralization ages, the metallogenesis of this province has long been a matter of debate. In this study, molybdenite Re-Os, pyrite Re-Os, and Rb-Sr isotope methods are used to date the Yinachang and E’touchang Fe-Cu deposits in the central part of this province. Fine-grained (〈0.1 mm) molybdenite occurs as veinlets along bandings or fractures of magnetite ores and hydrothermal veins in the Yinachang deposit. Molybdenite separates from magnetite ores have highly reproducible Re-Os model ages of 1654 ± 7 Ma, whereas those from hydrothermal veins have a much younger Re-Os model age of 1451 ± 6 Ma. Euhedral pyrite grains occur locally along foliations of hematite ores and their proximal alteration assemblages in the E’touchang deposit. Pyrite separates have an Re-Os isochron age of 1487 ± 110 Ma and a single-grain Rb-Sr isochron age of 1453 ± 28 Ma, both of which are compatible with the molybdenite Re-Os age of hydrothermal veins from the Yinachang deposit. The molybdenite age of magnetite ores is in good agreement with zircon U-Pb ages of dolerite intrusions in the region, and is considered to represent the timing of a major ore formation event at ~1655 Ma. The younger Re-Os and Rb-Sr ages likely record a secondary hydrothermal overprint event at ~1450 Ma, which has not been recognized before. The mineralization potential and implications of this event need to be investigated in future studies. Our new isotopic data set hence demonstrates that the Kangdian IOCG deposits were likely formed at ~1655 Ma, synchronous with the late Paleoproterozoic intracontinental rifting event of the western Yangtze block.