It's a popular belief that a fish's memory lasts for only seven seconds. It may seem sad to think that they don't remember what they've eaten or where they've been, and they don't recognize you or any of their friends — every moment in their life would be like seeing the world for the first time.

    But don't be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago.

    In the study, researchers from MacEwan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again.

    Researchers used computer software to monitor the fish's movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

    In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively（挑衅地） in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

    Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild.

    “If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamilton told Live Science.

    For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

    Say you're in the supermarket parking lot，holding your baby，bags of goods，and trying to open your car. A stranger walks up and says，" Here，let me hold your baby." Should you let him?

    According to a new New York University study，knowing whether or not to trust someone is so important that we can tell whether a face is trustworthy before we even consciously know it's there. The researchers knew from previous studies that people are fairly similar when it comes to how they judge a face's trustworthiness. They wanted to find out whether that would be true if people only saw a face for a quick moment—an amount of time so short that it would prevent making a conscious judgment.

    To carry out their study，the researchers monitored the amygdala (扁桃腺结构) of 37 volunteers while showing them 300 faces for 33 milliseconds each. Those faces had already been tested with a different set of 10 subjects，who saw them for much longer. In those earlier tests，people agreed about whether to trust each face. In this new study，fascinatingly，different parts of the amygdala lit up when a subject saw an untrustworthy face and a trustworthy one—and it lit up more when the face in question was suspicious (可疑的).

    " Faces that appear likely to cause harm are suddenly tracked by the amygdala，so it could then quickly change other brain processes and make fast responses to people—approach or avoid，" says Jon Freeman，the study's senior author. "Our talents for making instant judgments could either come from birth or be learned from the social environment."

    So should you trust the guy in the parking lot? Your brain already knows.

    Cao Yuan, a PhD student from China, had two papers published on strange behaviour in atom-thick layers of carbon that have opened up a new field of physics.

    Pablo Jarillo-Herrero's group at MIT was already layering and rotating (旋转) sheets of carbon at different angles when Cao joined the lab in 2014. Cao's job was to find out what happened when one graphene (石墨烯) sheet was twisted only slightly wiht respect to the other, which one theory predicted would thoroughly change the material's behaviour.

    Many physicists doubted the idea. But when Cao set out to create the subtly twisted stacks, he spotted something strange. Exposed to a small electric field and cooled to 1.7 degrees above absolute zero, the graphene—which ordinarily conducts electricity—became an insulator. That by itself was surprising. But the best was yet to come: with a slight change to the field, the twisted sheets became a superconductor, in which electricity flowed without resistance.

    The ability to get atom-thick carbon into a complex electronic state through a simple rotation now has physics demanding to engineer exciting behavior in other twisted 2D materials. Some even hope that graphene could shed light on how more-complex materials superconduct at much higher temperatures. "There are so many things we can do," says Cory Dean, a physicist at Columbia University. "The opportunities at hand now are almost irresistible."

    Hitting graphene's “magic angle”—a rotation between parallel sheets of around 1.1°—involved some trial and error, but Cao was soon able to do it reliably. His experimental skill was extremely important, says his supervisor Jarillo-Herrero. Cao pioneered a method of tearing a single sheet of graphene so that he could create a stack of two layers, from which he could then fine-tune alignment (微调校准).

    Cao loves to take things apart and rebuild them. A heart, he is “a tinkerer”, his supervisor says. On his own time, this means photographing the night sky using homemade cameras and telescopes—pieces of which usually lie across Cao's office. "Every ime I go in, it's a huge mess, with computers taken apart and pieces of telescope all over his desk," says Jarillo-Herrero.

    What's best to read this year?

    Secrets I Know (Random House Children's Books, ages 3-7)

    This tale written by Kallie George and pictured by Paola Zakimi follows a young girl and her little friend as they move from rain to sunshine, from pleasant loneliness to sweet friendship, and finally from adventures on earth to an exploration of the sky above. The colors of Zakimi's pencildrawings are calming and George's poetic text tells her story with simple language.

    Pandora (Clarion Books, ages 3-7)

    The award-winning author Victoria Turnbull tells the story of a little fox Pandora. Pandora lives alone. She makes herself a handsome home, but no one ever comes to visit. Then one day something falls from the sky -- a bird with a broken wing. Little by little, the bird helps Pandora feel less lonely. Turnbull's watercolor and colored pencil drawings make this story of friendship and growth an atmospheric delight.

    Prince and Pirate (G.P. Putnam's Sons Books for Younger Readers, ages 5-8)

    A different kind of friendship is described in this book, by Charlotte Gunnufson with pictures by Mike Lowery. Prince and Pirate are a pair of mismatched fish put into the same aquarium（水族馆). At first it seems that they'll never learn to be friends. It's only when both take pity on a frightened dogfish that they learn the benefits of cooperation, and soon all three fish become good friends.

    The Giant Jumperee (Dinal Books, ages 3-5)

    The story was written by the award-winning British author Julia Donaldson. When Rabbit hears a loud voice bellowing（吼叫）threateningly from inside a cave, he gathers Cat, Bear and Elephant to help him decide what to do. But it's Mama Frog who fearlessly confronts（面对）the unknown creature. Helen Oxenbury's soft watercolors creat a beautiful countryside and her characterizations of the animals are impressive.

Kindle E-reader, 8th generation

    Free Touchscreen Display

    Price: $79. 99

    ● Thin and light for one-handed reading

    New Kindle is 11% thinner and 16% lighter than the previous generation Kindle, making it easy and comfortable to hold in one hand.

    ● Read like real Paper

    Kindle creates text similar to what you see in a physical book. The blacks and whites on the screen are uniform, improving text and image quality.

    ●Long-life battery

    Kindle doesn't need power to show a page of text, allowing you to read for weeks on a single charge.

    ● Thousands of books, no distraction (分心)

    Kindle is designed to be an e-reader. It satisfies your love of reading without interruptions like e-mails and phone calls.

    ●Look it up without leaving your page

    Smart Lookup combines entries from The New Oxford American Dictionary with information from Wikipedia, so you can know meanings, characters and more without losing your place.

    ●Adjust your text size

    Choose from eight text sizes to prevent tired eyes, so you can keep reading longer.

    Customer reviews:

    ※ Damon, May 21, 2019

    The price is great with an extra $ 20 off and this new Kindle is smaller in my hands than my old one. I was sad to lose my old Kindle, but this one is terrific.

    ※ Jason, January 26, 2019

    I miss the original Kindlers size—this one is too small. Also, the screen is overly sensitive and things pop up (弹出) and the battery doesn't last as long as the original Kindle. But my biggest disappointment is that this Kindle doesn't allow you to transfer everything from the original Kindle、so I lost all of the information from my old one. Overall, disappointing.

    ※ Susan, November 17, 2018

    I had the original Kindle, and the battery lasted for weeks. This battery only seems to last a few days, however. The other problem I have with this version of the Kindle is the touch screen. It is annoying when you are reading and start turning the wrong way. Sometimes, it's hard to get the page to turn the way you'd like it to.

"Don't get dirty!" was once often shouted by parents angrily watching their children ruin their best clothes. It was unavoidable that children's whites would turn brown before the day was over. 

Today, many parents may secretly wish their children had the chance to pick up a bit of dirt. With the rise of city life, and the attraction of video games and social media, contact with nature is much less than in the past. For many, there is simply no opportunity to get muddy. According to recent research, the dirt outside is teaming with friendly microorganisms (微生物) that can train the immune (免疫的) system and build the body against illnesses, such as anxiety. 

These findings show that outdoor exercise is not only beneficial because of the chance to run around free—but that certain natural materials, such as soil and mud, also have powerful microorganisms which have positive effect on children's health. Outdoor play can also offer valuable learning experiences. For example, the act of rubbing and shaping materials like mud or sand can help children develop their senses and movement. 

Such activities—away from the house or classroom—may also help children to find ways to deal with emotions that may be hard to explore in other environments. So-called "Sandtray Therapy (沙盘疗法)", which includes using sand to express one's thoughts and feelings, is an accepted form of guidance for children who are struggling to speak out their inner emotions. 

Surprisingly, people who spent most of their childhood in the countryside show a better reply to stressful events like public speaking compared with those who grew up in cities. "The people who grew up in cities are kind of ‘walking time bombs' when facing the stress we meet today. However, people who have spent lots of time in nature since childhood are generally stronger in recovery and more positive." says Christopher Lowry, a professor of University of Colorado Boulder.