天天棋牌游戏大厅官方版

September 2020
Vol 6, Issue 36

梅花棋牌

天久棋牌

ONLINE COVER As nations worldwide have instituted mask mandates to curb the spread of COVID-19, global commercial suppliers have encountered shortages in the face of unprecedented demand. To compensate, many people have turned to homemade masks and mask alternatives, but these do-it-yourself versions have not been tested systematically. To evaluate the effectiveness of 14 different types of masks and other frequently substituted face coverings, Fischer et al. designed a simple approach in which either one male speaker or, in some cases, four speakers wore each mask while standing in a dark enclosure. The speaker would say the phrase "stay healthy, people" five times in the direction of a laser beam, which scattered light from the droplets released during speech. A cell phone camera recorded the droplets and a simple computer algorithm counted them. The setup was intentionally designed to be simple and inexpensive so it could be replicated by non-experts. While the authors note their work is still in the early stages, and their method has so far only been tested in a small group of people, these preliminary, proof-of-principle findings suggest that professional-grade N95 masks, surgical or polypropylene masks, and handmade cotton masks may all block much of the spray produced when wearers speak. The early findings suggest that bandanas and neck fleeces (like balaclavas), however, likely provide little protection. [CREDIT: Viktoria Kazakova/Shutterstock adapted by C. SMITH/SCIENCE ADVANCES]