Alkaline decomposition of pentathionate has been investigated by high-performance liquid chromatography, which allows us to track different sulfur-containing species simultaneously in the presence of a carbonate/hydrogen carbonate buffer at 25.0 ± 0.1 °C and at a constant ionic strength. It has been shown that, besides the major product, thiosulfate, not only tetrathionate but also hexathionate appears in significant amounts during the course of the reaction. At higher pHs, both of them are unstable long-lived intermediates because of their well-known alkaline degradation, but a decrease of the pH increases their stability (especially that of tetrathionate), meaning that they may even become end products. On the basis of these observations, a 10-step kinetic model with five fitted and five fixed rate coefficients is suggested and discussed to take all of the most important characteristics of the decomposition into account. We have also demonstrated and discussed that the well-known thiosulfate-assisted rearrangement of pentathionate leading to hexathionate might only play a very minor role in the formation of hexathionate under our experimental conditions.

In this paper, an impedance matching underwater acoustic bend with pentamode microstructure is designed. The proposed bend is assembled by pentamode lattice. The effective density and compressive modulus of each unit cell can be tuned simultaneously, which are modulated to guarantee both the bending effect and high transmission. The standard deviations (SDs) of transmitted phase are calculated to quantitatively evaluate the degree of the distortion of the transmitted wavefront, while the transmission is calculated to appraise the degree of acoustic impedance matching. The low SDs and high transmission indicate that the designed bend has a nice broadband bending effect and is impedance-matched to water. This design has potential applications in underwater communication and underwater detection.

The thiosulfate-bromate reaction has been studied by high-performance liquid chromatography, monitoring the concentrations of thiosulfate and tetrathionate simultaneously. It is found that concentration-time curves of both species display a sigmoidal shape in a slightly acidic, well-buffered medium. Unlike the previously reported complex reaction systems involving bromate, this nonlinear dynamical behavior originates from neither proton nor bromine(III) autocatalysis under our experimental conditions. We demonstrated that sulfur(IV) species significantly accelerates the reaction; therefore, it acts as an autocatalyst. To the best of our knowledge, no reaction system has yet been reported among the pH-driven oxysulfur-oxyhalogen systems, where sulfur(IV) has such a remarkable role. On the basis of the simultaneous evaluation of [S2O3(2-)] and [S4O6(2-)] time series, an eight-step kinetic model is proposed to account for the experimental observations. The model employed here may serve as a solid starting point to extend it for other oxysulfur-oxyhalogen systems where such a seemingly general phenomenon may become observable.

This paper reports the geochemical compositions of coals and non-coal samples from a complete seam section in the Late Permian Longtan Formation from the Yueliangtian mine, western Guizhou, southwestern China. The abundances, modes of occurrence, and origin of elements and minerals in the Yueliangtian coal were investigated using optical microscopy, scanning electron microscopy with an energy dispersive X-ray spectrometer, X-ray powder diffraction, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The host rocks (roof and floor) and one parting sample of the coal seam have high TiO2 contents, which is in accordance with the high TiO2 content in the Emeishan basalt from the Kangdian Upland. The coal bench samples are rich in SiO2 (14.52%, whole-coal basis) compared with the average for the common Chinese coals, and the high SiO2 present in this study is consistent with the abundant quartz, which was mainly precipitated from siliceous solutions produced by weathering of the Emeishan basalt. Compared to the average values for world hard coals, the coal bench samples are enriched in V (77.0 μg/g), Cu (41.9 μg/g), Se (4.77 μg/g), Zr (93.8 μg/g), Hg (0.375 μg/g), and Pb (21.4 μg/g). In contrast to many other Permian coals from southwestern China, the transition elements, including Cr, Co, Ni, and Zn, are not enriched in the coal bench samples, possibly due to the input of the terrigenous materials with felsic and felsic-intermediate rock compositions. The highfield strength elements are relatively enriched not only in the parting samples but also in the adjacent coal bench samples, indicating that the partings were subjected to leaching by groundwater during the diagenetic process. Elements in coal, including B, Cr, Co, Zn, and Ni, are mainly associated with clay minerals, while As, Se, Sb, and Pb mainly occur in sulfide minerals (pyrite and marcasite). An intra-seam volcanic ash-derived tonstein layer identified in the coal is characterized by strong negative Eu anomaly in the Upper Continental Crust-normalized rare earth elements and Y distribution pattern, indicating the input of felsic or felsic-intermediate terrigenous materials.