2 . A team in Europe are working with wood, but not in the usual ways. They are not carpenters (木匠). Instead, they are scientists exploring how wood can lead to a greener electronic device, a transistor (晶体管) made from balsa wood, whose production releases less climate-warming gas into the air.

Transistors play an important role in computers and other devices. They act like tiny switches to control the flow of electricity. Engineers use them to process and store data. Today’s laptops may host billions of them. So they must be tiny — only a little wider than a strand of DNA.

The new transistor being built by physicist Isak Engquist and his team at Sweden’s Linkoping University isn’t as small as those. Big enough to see and hold, it can stand only an electric pressure that pushes electrons along. And it controls a current using charged particles (粒子) called ions.

This new technology shows a “proof of concept” that the idea can work, even if the new device is not yet ready to put into today’s electronics. “While it seems large by today’s standards, such a transistor still might prove useful for electronics that require low electric pressures,” says Engquist.

“The new transistor suggests that future electronic devices might be made in living plants,” Daniel Simon, a physicist in the team, says. “Imagine peeling away some bark from a living tree,” he says, “and stamping electronic circuits into the living wood.”

In fact, Engquist says, “There are so many ways we can use wood and the components of wood that we would never have thought of.” For instance, he can now imagine a wood-based sensor that could monitor crop health, measure pollution or survey a forest for fire risk.

3 . Young people are spending more time in digital spaces. The Internet allows us to connect with people, share ideas, be creative, have fun and discover new things. Unfortunately, young people also face risks online. Common problems include cyberbullying (网络欺凌), receiving unwanted messages, seeing images and content you don’t want to see, or having your private information or photos shared without your permission.

Safer Internet Day (SID) is organized in the second week of February every year, and over 180 countries take part. The aim is to raise awareness of online issues and make the Internet a safer place. SID invites everyone to be part of a big conversation about online issues. This is particularly important for teenagers because they often experience unpleasant situations online, but they don’t always feel they can talk about them.

Cyberbullying is when someone uses the Internet to embarrass, threaten or hurt another person. If you experience cyberbullying, talk to an adult you trust as soon as possible. Don’t reply to any messages but save the evidence.

Going online often means spending time alone. When you feel down, social media can make you feel lonelier. Using social media might be related to higher levels of depression. So you need healthy social media use.

Whatever app you use, make sure you know who sees your posts and personal information. Limit what people can see, decide who can comment on your content and thwart other users’ comment. It may be illegal to share a photo or video of someone without their permission. The SID’s website has advice about what to do if someone shares pictures of you that you feel embarrassed about.

There is still a lot we don’t know about how time spent online affects people’s well-being. But talking about all the issues helps everyone understand common problems and know how to deal with them.