[en] The fate of a subducted slab is a key ingredient in the context of plate tectonics, yet it remains enigmatic especially in terms of its crustal component. In this study, our efforts are devoted to resolve slab-related structures in the mid-mantle below eastern Indonesia, the Izu–Bonin region, and the Peru area by employing seismic array analysing techniques on high-frequency waveform data from F-net in Japan and the Alaska regional network and the USArray in North America. A pronounced arrival after the direct P wave is observed in the recordings of four deep earthquakes (depths greater than 400 km) from three subduction systems including the Philippines, the Izu–Bonin, and the Peru. This later arrival displays a slightly lower slowness compared to the direct P wave and its back-azimuth deviates somewhat from the great-circle direction. We explain it as an S-to-P conversion at a deep scatterer below the sources in the source region. In total, five scatterers are seen at depths ranging from ~930 to 1500 km. Those scatterers appear to be characterised by an ~7 km-thick low-velocity layer compared to the ambient mantle. Combined evidence from published mineral physical analysis suggests that past subducted oceanic crust, possibly fragmented, is most likely responsible for these thin-layer compositional heterogeneities trapped in the mid-mantle beneath the study regions. Our observations give a clue to the potential fate of subducted oceanic crust.

[en] Two kind of technologies, including instrumental and chemical methods, were used to determine the valence states of trace vanadium in the aerosol and sedimentation produced in the explosive experiments. The main composition of the samples were provided by XRF (X-ray fluorescence spectrometry) test which was first applied as a method not damaging the samples. The results of XPS are in agreement with those provided by XRF method and moreover indicated the dominating valence states of vanadium existing in V⁵⁺. Titration Determination was proved not feasible to the determination of trace vanadium as its concentration was less than the detection limit of the method. The kinetics spectrophotometry method was used to the determination of trace vanadium in the aerosol and sedimentation and exhibited excellent precision and accuracy on the measurement of sedimentation. However, the detection of vanadium in the aerosol with the kinetics method was interfered by the dissolution of the sampling film. (authors)

[en] A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at both room temperature and low temperatures. Experimental measurement shows the temperature-dependent conductivity of the ZnO nanowire at low temperatures (below 100 K). The further theoretical analysis confirms that weak localization plays an important role in the electrical transport, which is attributed to the surface states induced by plenty of oxygen vacancies in ZnO nanowire. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] Highlights: • Surface strain of Ni and NiO was engineered to regulate the d-band structure. • DFT calculations found that the Ni(111) supported NiO(111) and NiO(100) supported Ni(100) show shifted d-band centers. • Guided by the DFT calculation, the synthesized Ni-NiO catalysts show considerably enhanced HER activity. -- Abstract: Electrolysis of water in alkaline media to produce hydrogen is a green and promising energy storage technology, but the kinetically sluggish hydrogen evolution reaction (HER) in alkaline electrolytes limits its development, requiring cheap and highly efficient catalysts to increase the HER rate. The HER activity of transition metal-based catalysts is closely associated with the d-band structures. Herein, the surface strain of Ni and NiO was engineered to regulate the d-band centers and the HER activity. DFT calculations found that the Ni(111) supported NiO(111) shows expanded surface lattice compared to the unsupported NiO(111), and the NiO(100) supported Ni(100) shows compressed surface lattice compared to the unsupported Ni(100), leading to ∼2 eV upshift and downshift of d-band centers of the surface Ni atoms, respectively. Guided by the DFT calculation, the surface-oxidized Ni (so-Ni) and surface-reduced NiO (sr-NiO) catalysts were synthesized and shows expanded and compressed surface lattice respectively, leading to enhanced HER activity. The synthesized sr-NiO shows the highest HER activity with an overpotential of 164 mV to deliver a current density of 10 mA cm⁻², which outperforms many of the recently reported Ni-based HER catalysts in alkaline electrolytes.

[en] The status of technical efficiency (TE) of environmental protection enterprises is crucial to the sustainable economic development. Based on the micro-survey data of China’s environmental protection enterprises from 2003 to 2013, through a systematic calculation and comparison about TE level under stochastic frontier analysis, this article investigated the distribution characteristics and heterogeneous sources of them comprehensively and found that first, there are wide-ranging technical efficiency differences among sub-sectors, ownership, and regions within China’s environmental protection industry, and this type of heterogeneity was significantly interfered by the institution and policy environment. Second, there is obvious scale economy effect and no scope economy effect in the TE distribution of China’s environmental protection enterprises, and their TE level has a positive response to management improvement and competition enhancement, but has a negative feedback on heavy asset expansion and debt-driven growth mode. Third, the overall TE levels of non-state-owned enterprises are higher than that of state-owned enterprises; the overall TE levels of enterprises located in the eastern provinces are higher than those of enterprises located in the central and western provinces. Fourth, reducing tax burdens of environmental protection enterprises is more effective to promote their TE level than providing governmental subsidies directly. Therefore, to promote the quality of the development for China’s environmental protection industry, it is necessary to emphasize the market mechanism. Based on the market power, we should accelerate the industry integration, cultivate the market demand, and promote market competition. Furthermore, the government should also need to design a targeted support system and differentiated policy arrangements for the development of environmental protection enterprises.

[en] A circular polarizer is proposed based on a single layered metasurface. This metasurface circular polarizer is composed of L-shaped nanoholes etched on the silver film. The L-shaped nanoholes are rotational symmetric, and the special symmetric structure determines the polarization selection transmission of the metasurface. The theoretical analysis elaborates the design process of the metasurface circular polarizer. The proposed metasurface circular polarizers have good polarization selective transmittance, and more interestingly, they take on the opposite circular dichroism at different wavebands. The numerical simulations and experiment measurement confirm the circular dichroism of the proposed circular polarizers. The compact design, ultrathin thickness and available performance can expand the applications of the metasurface circular polarizers in the integrated optics. (paper)

[en] Several metasurface diffraction-free beam generators are designed by using a set of resonant V-shaped nanoholes. Cosine beams, Bessel beams and cosine Bessel beams are generated through the corresponding metasurface structures with V-shaped nanoholes arranged in different ways. Theoretical analysis provides the design mechanism for these diffraction-free beam generators, numerical simulations and experiment measurement give the powerful verification for the generation of diffraction-free beams. The proposed diffraction-free beam generators have advantages of ultra-thin thickness, compact structure, ease to manufacture and flexibility to operate. The generated diffraction-free beams show high efficiency, polarization independence and validity for any visible wavelength. The compact design is benefit to the applications of diffraction-free beams in nanometer fabrication, optical integrated imaging and optical micromanipulation. (paper)

[en] Highlights: • XPS method proved that Mn and S exist as positive divalent(Mn²⁺) and negative divalent(S^2-), respectively at the gas-slag interface. • Comparing XPS and Raman, the structure of the CaO-SiO₂-MnO slag has a gradient change trend from the interface to the body due to uneven distributions of elements. • Mn and S have a strong correlation, which is due to the existence of Mn cluster and the uneven distribution of charges. -- Abstract: In this work, the interfacial element distribution and structure of CaO-SiO₂-10%mass MnO slag was explored using the gas-slag equilibrium experimental method and XPS detection method at the temperature of 1873 K. Based on the full spectrum, the relative content of sulfur gradually decreases, the manganese has the same trend, while the calcium content keeps increasing. According to the analysis of the Mn2p and S2p spectra, it indicated that Mn and S exist as positive divalent (Mn²⁺) and negative divalent (S^2-), respectively. The O1s fitting result indicates that the proportion of non-bridged oxygen (O^-) increased, while that of bridged oxygen (O⁰) decreased with the etching time increased. The structural units obtained by Raman spectroscopy are closer to the evaluation data of the CaO-SiO₂ system, while the interfacial structure information tends to the MnO-SiO₂ system. Although CaS is thermodynamically more stable than MnS, the reason for the sulfur accumulation in the gas-slag interface is due to the d electron supplement from Mn. Thus, the concept of interface sulfide capacity is proposed. As the etching depth increases, the interface sulfide capacity decreases continuously. Comparing XPS and Raman, the structure has a gradient change trend at the gas-slag interface, which confirms the presence of the boundary layer at the gas-slag interface.

[en] Different sampling and different injection method were used during analyzing unknown detonation products in a obturator. The sample analyzed by gas chromatography and gas chromatography/mass spectrum. Qualitative analysis was used with CO, NO, C₂H₂, C₆H₆ and so on, qualitative analysis was used with C₃H₅N, C₁₀H₁₀, C₈H₈N₂ and so on. The method used in the article is feasible. The results show that the component of detonation in the study is negative oxygen balance, there were many pollutants in the detonation products. (authors)

[en] Vanadium slag usually contains 13.52-19.03 mass % V₂O₃ and 6.92-14.35 mass % TiO₂. The V in vanadium slag is effectively extracted by traditional methods, whereas Ti, a valuable metal, cannot be used. To effectively utilize the Ti, a new method for preparing TiO₂ from vanadium slag via AlCl₃ chlorination-TiCl₄ hydrolysis was proposed in this work. The chlorination of Ti in vanadium slag, thermodynamics of hydrolysis of metal chlorides (TiCl₄ and AlCl₃), and hydrolysis of chlorides were investigated. Rutile TiO₂ containing a small amount of impurities (1.58 mass % Al and 2.03 mass % Cl) was synthesized. (author)