The first C3-dicarbonylation of indoles was realized through direct oxidative cross-coupling of indoles with methyl ketones in the presence of molecular iodine and pyrrolidine. This reaction constructed a highly efficient indolyl diketones scaffold, which might be regarded as a useful biological and pharmacological tool in the exploration of therapeutic A2BAR modulators. The use of inexpensive molecular iodine and pyrrolidine and a broad substrate scope make this protocol very practical. Preliminary mechanistic studies indicate that two paths are involved in this process.
The gas-insulated switchgear (GIS) has been widely used in modern ultra-high voltage systems. However, once it fails, its fully enclosed feature brings challenges in its diagnosis and maintenance. As the failure rate of GIS due to insulator failure has been increasing in recent years, it is necessary and important to understand the commonly existing defects presented in the insulator. First, the manufacturing process of GIS insulators is introduced here. The defect types commonly existing in the insulator are categorised. The failure of GIS due to insulator defects that occurred in recent years are reviewed and discussed. The content in this study is useful for engineers and scientists to study on the GIS solid insulation defects and their failure mechanisms.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
The effect of fluid flow on eutectic microstructure is systematically examined in Al-Cu alloys of compositions varying from 19.5 to 45.0 wt pct Cu. It is shown that significantly different fluid-flow effects are present in hypo-and hypereutectic alloys, since the modes of convection are different in these two cases. In hypoeutectic alloys, the rejected solute is copper, which is heavier than aluminum, and fluid flow gives rise to radial solute segregation in cylindrical samples. In hypereutectic alloys, a lighter aluminum is rejected that causes a double diffusive convection and gives rise to macrosegregation. These composition variations are shown to produce nonuniform microstructures that vary either radially (in hypoeutectic alloys) or axially (in hypereutectic alloys) and can give rise to a single phase-toeutectic, lamellar-to-rod eutectic, or rod-to-lamellar eutectic transition in a given sample. Composition measurements are carried out to characterize solute segregation due to fluid flow. The fluid-flow effect on eutectic spacing in eutectic or near-eutectic alloys is found to be very small, whereas it increases the eutectic spacing in hypoeutectic alloys for a given local composition and it can increase or decrease the spacing in hypereutectic alloys, depending on the microstructure and solidification fraction. Theoretical models, based on diffusive growth, are modified to predict the spatio-temporal variation in eutectic microstructure caused by fluid flow.
Key indicatorsSingle-crystal X-ray study T = 294 K Mean (C-C) = 0.007 Å R factor = 0.084 wR factor = 0.189 Data-to-parameter ratio = 13.0For details of how these key indicators were automatically derived from the article, see
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