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.
Some are wrapped up in scarves and woolly hats, while others are sitting in deckchairs, eating picnic lunches and playing music as they get ready to watch the chart-topping singer Raye in action.
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Yellow: Sub out
It is a live vaccine which means it contains a weakened version of the chickenpox virus. As such, it is not recommended for those with a compromised immune system because of an illness like HIV or as a result of treatment such as chemotherapy.
文 | 节点财经，作者 | 董轩