Highlights This paper analyzes the effects of COVID-19 on the U.S. stock market volatility at the industry level. The market switching AR model is used to identify regime change from lower volatility to higher volatility. Petroleum and natural gas, restaurants, hotels and lodgings industries exhibit large increases in risk. Machine learning (ML) feature selection methods are used to identify influential economic indicators. Changes in the volatility are found to be more sensitive to COVID-19 news than economic indicators.

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The purpose of this study was to compare the periapical tissue responses and cementum regeneration in response to three widely used root-end filling materials, amalgam, SuperEBA, and Mineral Trioxide Aggregate (MTA). These materials were placed using modern microsurgical techniques on endodontically treated dog premolars and molars. After 5 months, the cell and tissue reactions of surface-stained un-decalcified ground sections were evaluated by light microscopy and statistically analyzed. The major difference in the tissue responses to the three retrofilling materials were the degree of inflammation and types of inflammatory cells, number of fibrous capsule formations, cementum neoformation over these materials, osseous healing and resulting periodontal ligament thickness. MTA showed the most favorable periapical tissue response, with neoformation of cemental coverage over MTA. SuperEBA was superior to amalgam as a root-end filling material.