Hyperspectral unmixing aims at identifying the hidden spectral signatures (or endmembers) and their corresponding proportions (or abundances) from an observed hyperspectral scene. Many existing approaches to hyperspectral unmixing rely on the pure-pixel assumption, which may be violated for highly mixed data. A heuristic unmixing criterion without requiring the pure-pixel assumption has been reported by Craig: The endmember estimates are determined by the vertices of a minimum-volume simplex enclosing all the observed pixels. In this paper, using convex analysis, we show that the hyperspectral unmixing by Craig's criterion can be formulated as an optimization problem of finding a minimum-volume enclosing simplex (MVES). An algorithm that cyclically solves the MVES problem via linear programs (LPs) is also proposed. Some Monte Carlo simulations are provided to demonstrate the efficacy of the proposed MVES algorithm.

Hydrogel modified porous matrix with the super-wetting surface (i.e., superhydrophilic/underwater super-oleophobic) is ideal for oil/water separation. However, the deterioration in mechanical strength and separation efficiency during the swelling process and complicated synthesis procedure limits its industrial application. In this study, a strategy of using ethanol to dynamically regulate the hydrogen bond crosslinking between polyvinyl alcohol (PVA) and tannic acid (TA) is proposed to prepare a "hydrogel paint", which can be simply applied on the porous substrate surface by different one-step operations (dipping, brushing, spraying, etc.) without additional cross-linking. The underline mechanism is attributed to the re-establishment of intermolecular hydrogen bond mediated cross-linking between PVA and TA during ethanol evaporation. Consequently, the resultant hydrogel coating exhibits ultra-high strength (>10 MPa), swelling volume stability, and excellent oil-water separation efficiency (>99%). This study will provide new insights into the scalable fabrication of hydrogel-coated porous materials for oil/water separation in industrial scenarios.

We have developed for the first time a general, concise and highly selective method for the C2heteroarylation of pyridines and related azines with a broad range of heteroarenes via a two-fold C-H activation, which streamlines the previous approaches that require the activated azine N-oxide as the coupling partner.Scheme 1 Selected medicinal and natural molecules containing 2-heteroarylated pyridines.

Surface coatings can enhance the mechanical and functional properties of substrates and keep good balance between specific mechanical properties and sufficient surface performance of the components. Coatings composed of high entropy alloys (HEAs) and HEA‐based materials, including metallic, ceramics, and composites have attracted the global attention and developed rapidly over the last decade, owing to their outstanding properties. Here, the authors provide a critical review of the state‐of‐the‐art for HEA‐based coatings, aiming to address the related conceptions, designing principles, microstructural, and mechanical evolutions during fabrication and post‐treatments process. The surface properties which are not limited to anti‐corrosion, anti‐radiation, and anti‐diffusion and their underlying mechanisms are analyzed. The development tendency and future applications are classified and discussed, including the basic researches about HEAs, the regulations of fabrication techniques and the exploring of functional properties of HEA‐based coatings. Due to their superior mechanical and functional potentials as well as abundant element‐constitutions of designing, surface coatings composed of HEA‐based materials are considered to have promising applications in engineering and industrial manufacturing.

The aryl cycloaurated species are established as reliable models for understanding the gold(iii)-catalyzed oxidative cross-couplings between arenes and arylboronic acids.