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A concise total synthesis to generate synthetically challenging steroids scaffolds is reported utilizing palladium-catalyzed dearomatization cyclization for the key cyclization step, enabling the divergent synthesis of 6,6,6,5-tetracyclic steroids cores through both ligand and reaction condition control. We have started from the simple starting materials 2,4,6-trihydroxybenzoic acid and 2-methylcyclopentane-1,3-dione to selectively generate complex steroid scaffolds in a 12-step operation. [ABSTRACT FROM AUTHOR]

The impact of supercritical CO2/H2O technology on the threshold-voltage instability of AlGaN/GaN metal-insulator semiconductor high-electron-mobility transistors (MIS-HEMTs) is investigated. The MIS-HEMTs were placed in a supercritical fluid system chamber at 150 °C for 3 h. The chamber was injected with CO2 and H2O at pressure of 3000 psi (1 psi ≈ 6.895 kPa). Supercritical H2O fluid has the characteristics of liquid H2O and gaseous H2O at the same time, that is, high penetration and high solubility. In addition, OH− produced by ionization of H2O can fill the nitrogen vacancy near the Si3N4/GaN/AlGaN interface caused by high temperature process. After supercritical CO2/H2O treatment, the threshold voltage shift is reduced from 1 V to 0.3 V. The result shows that the threshold voltage shift of MIS-HEMTs could be suppressed by supercritical CO2/H2O treatment. [ABSTRACT FROM AUTHOR]