The Asian country announced yesterday that China was putting tariffs or taxes on about $3 billion worth of imports from the U.S. The tariffs are on 128 American-made products, ranging from pork and fruit to steel pipes. This will make it more expensive for America businesses to sell those products in China. And China says this was done as a response to the tariffs that the U.S. recently put on imports of Chinese steel and aluminum.

    Meanwhile, U.S. President Donald Trump says more tariffs, new ones worth as much a $50 billion are being planned by the U.S. on additional goods from China. So, one big question is, will all this cause a trade war, when countries take turns putting tariffs on each other 's goods, causing prices to rise?

    We don't know yet. The U.S. and China ship hundreds of billions of dollars of goods back and forth every year. So, the tariffs we've seen so far are a tiny part of that. And America's treasury secretary says the U.S. and China are talking behind the scenes about how to prevent a possible trade war.

    But a number of experts are concerned this could turn into one and so are some stock investors. The Chinese tariffs were a major factor in a drop of the U.S. stock market yesterday when the Dow Jones Industrial Average fell 459 points. But just like it's hard to tell if a trade war is on the horizon, it's also hard to tell what kind of effects one could have decades down the road.

    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.

    Students perform less well in final exams if smartphones are allowed in class, for non-academic (非学业的) purposes in lectures, a new study in Educational Psychology finds. Students who don't use smartphones themselves but attend lectures where their use is acceptable also do worse, suggesting that smartphone use damages the group learning environment.

    Researchers from Rutgers University in the US performed an in-class experiment to lest whether dividing attention between smartphones and the lecturer during the class affected students' performance in within-lecture tests and a final exam. 118 students at Rutgers University took part in the experiment during one term of their course. Smartphones were not allowed in half of the lectures and allowed in the other half. When smartphones were allowed, students were asked to record whether they had used them for non-academic purposes during the lecture.

    The study found that having a smartphone didn't lower students' scores in comprehension tests within lectures, but it did lower scores in the final exam by at least 5%, or half a grade. This finding shows for the first time that the main effect of divided attention in the classroom is on the length of time in keeping memory, with fewer things of a study task later remembered. In addition, when the use of smartphones was allowed in class, performance was also poorer for students who did not use them as well as for those who did.

    The study's lead author, Professor Arnold Glass, added: "These findings should alarm students and teachers that dividing attention is having a not obvious but harmful effect that is damaging their exam performance and final grade. To help manage the use of smartphones in the classroom, teachers should explain to students the alarming effect—not only for themselves, but for the whole class."

    This is the first-ever study in an actual classroom showing a relationship between losing attention from smartphones and exam performance. However, more researches are required to see how students are affected by using smartphones after school.

    That people often experience trouble sleeping in a different bed in unfamiliar surroundings is a phenomenon known as the 4Tirst-nighf, effect. If a person stays in the same room the following night they tend to sleep more soundly. Yuka Sasaki and her colleagues at Brown University set out to investigate the origins of this effect.

    Dr. Sasaki knew the first-night effect probably has something to do with how humans evolved.

    The puzzle was what benefit would be gained from it when performance might be affected the following day. She also knew from previous work conducted on birds and dolphins that these animals put half of their brains to sleep at a time so that they can rest while remaining alert enough to avoid predators (捕食者). This led her to wonder if people might be doing the same thing. To take a closer look, her team studied 35 healthy people as they slept in the unfamiliar environment of the university's Department of Psychological Sciences. The participants each slept in the department for two nights and were carefully monitored with techniques that looked at the activity of their brains. Dr. Sasaki found, as expected, the participants slept less well on their first night than they did on their second, taking more than twice as long to fall asleep and sleeping less overall. During deep sleep, the participants' brains behaved in a similar manner seen in birds and dolphins. On the first night only, the left hemispheres (半球) of their brains did not sleep nearly as deeply as their right hemispheres did.

    Curious if the left hemispheres were indeed remaining awake to process information detected in the surrounding environment, Dr. Sasaki re-ran the experiment while presenting the sleeping participants with a mix of regularly timed beeps (蜂鸣声) of the same tone and irregular beeps of a different tone during the night. She worked out that, if the left hemisphere was staying alert to keep guard in a strange environment, then it would react to the irregular beeps by stirring people from sleep and would ignore the regularly timed ones. This is precisely what she found.

    Every year in May, art galleries and museums prepare shows to honor Leonardo Da Vinci, who died in France on May 2, 1519. He is remembered as one of the greatest artists and creative thinkers of all time. His most famous paintings are The Mona Lisa and The Last Supper.

    Recently, researchers have been studying a painting-Landscape 8P which, they think, is Da Vinci's earliest-known artwork. They used special lighting to study the artwork and discovered there were two images(图像), not one. One drawing is on the back of the piece, which dates back to August 5, 1473.

    The drawing on the front was painted when Leonardo was 21 years old. It shows a river valley and a castle outside the city of Florence. There is little left of the drawing on the back, perhaps because it was wiped off. Only a bridge over a river can be seen. But there is writing on both sides.

    The writing on the front gives the date and goes from right to left. Some people would call this "mirror-writing". It's a way Leonardo often wrote in his notebooks. The writing on the back goes from left to right and tells about an agreement, probably to produce a work of art.

    Cecilia Frosinini is an art historian. She said, "Leonardo was born left-handed, but was taught to write with his right hand from a very young age. By looking at his writings, including from this drawing, we can see his right-handed handwriting is educated and well done. "

    Experts compared the two handwriting samples(样本)and said they were both made by Leonardo. They show he could write well using his left hand or his right hand.

    The drawing is known as Landscape 8P from its number in an art list. It will be part of an exhibit at Italy's Uffizi Gallery. The gallery director, Eike Schmidt, said by studying the drawing researchers gave us a new way of looking at Leonardo's drawing technique and his abilities in writing.

Parties and social gatherings no longer excite us the same way they once did. This is not due to a lack of desire to socialize, but the smartphone.

At parties, people focus more on their smartphones than on their drinks. According to a recent study from International Data Corporation，over half of all Americans have a smartphone and reach it the moment they wake up, keeping it in hand all day. In addition, too many people are using smartphones while driving and as a result, they get into car crashes. 34 percent of teens admit to text while driving, and they confirm that texting messages are the major interruption while driving. People's attachment (依恋) to their smartphones is unbelievably becoming more important than the lives of themselves and others.

Just as drivers dismiss the importance of focusing while on the road, many people also fail to recognize the significance of human interaction. When with their friends, some people pointlessly (无谓地) check or send messages in the presence of their friends., which means that their friends are less important. In addition, relying on our smartphones to make friends does not give us the same advantages as making new friends in the real world. Face-to-face conversations will give us the chance to improve our communication skills in the long run.

As many people risk their lives and the lives of people around them just to send a text or mindlessly check their messages, smartphones are in many ways more dangerous to people. The technology shows the achievement weaken the value of communication. Not only is the smartphone affecting our desire to interact face to face, but it is also lowering people's ability to communicate.