Leonardo da Vinci is usually credited with conducting the first systematic study of friction in the late 15th century, a subfield now known as tribology that deals with the dynamics of interacting surfaces in relative motion. Da Vinci's notebooks depict how he pulled rows of blocks using weights and pulleys, an approach that is still used in frictional studies today, as well as examining the friction produced in screw threads, wheels, and axles. The authors of this latest paper used an experimental setup similar to da Vinci's.
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Фото: Павел Львов / РИА Новости
A widespread bacterial defence system called SNIPE is shown to localize to the cell membrane, where it identifies and cleaves the DNA of infecting phage as it is injected into the bacterial cell.