JERUSALEM—Israel's Environmental Protection Ministry asked citizens Wednesday to avoid unnecessary physical activity and stay indoors, as a serious sandstorm struck the Middle East in a thick yellow haze (霾) for a second day with no hope to see things clearly.

    The ministry said heavy levels of dust and sand in the air were a threat to cities throughout the country. The ministry's website advised pregnant women, the elderly and those with heart and respiratory (呼吸的) conditions to stay indoors, and asked schools to keep children indoors.

    The emergency service Magen David Adom reported that it has treated more than 300 Israelis suffering from breathing problems, and that hospitals have more respiratory-related patients, including a large number of the elderly and those with asthma and related conditions.

    The domestic Israeli airlines Arkia and Israir continued to ground their flights to Eilat because of reduced visibility.

    The sandstorm has affected Egypt, Jordan, Iraq, Lebanon and Syria, where at least five deaths have been reported.

    "There has been nothing that came close to the magnitude of this sandstorm," said Daniel Rosenfeld, a professor with the Institute of Earth Sciences at the Hebrew University in Jerusalem.

    "While Israel has experienced a number of sandstorms in the past, they started from the Sinai Desert and the Sahara Desert to the south and were joined by winter windstorms that cleared the air," he said. In this case, the storm comes from Syria and Iraq to the north and east.

    Because the storm is hitting during the summer, at a time of both little wind and severe heat and humidity, forecasters expect the particles to remain in the air throughout the weekend and possibly into next week.

    "This is really puzzling," said Rosenfeld, adding that he and his colleague will conduct research into the origins of the unprecedented (前所未有的) storm. (326 words)

    Wolves strike fear into the hearts of many species, humans included. Our fear of them has brought them to the edge of dying out, as we have cruelly killed them as competitors and trouble-makers. But researchers are discovering that the very fear they put into prey（被捕食者）species is exactly what helps make ecosystems（生态）healthy.

    Yellowstone National Park is a typical example of just how wolves can help repair an ecosystem. An October 2018 study analyzed 40 years of research on large animals inside the park.

    "Yellowstone has benefited from the reintroduction of wolves in ways that we did not anticipate, especially the complexity of biological interactions（互动） in the park," explained Mark Boyce, a professor in the Department of Biological Sciences." We were really surprised at that and we'd never have seen these responses if the park hadn't adopted ecological-process management—allowing natural ecological processes to take place with least human intervention."

    After the wolves were re-introduced at Yellowstone, willow and cottonwood trees increased in number. The population of bears and bison also rose and what was once a ruling deer-wolf interaction is now more diverse.

    To learn more about just how wolves are beneficial, a short documentary from Quest explains how the presence of wolves influences the behavior of deer, which eventually makes entire ecosystems more biologically diverse and healthy. In this documentary, biologist Aaron Wirsing explored why wolves and other top predators （捕食者）were needed for diverse ecosystems to develop. Using a simple video camera, Wirsing is gaining a unique view point on predator-prey relationships and changing the way we think about wolves.

    The research is one more piece of evidence for why protecting these top predators is important not just for wolves as a species, but for hundreds of species at every level of an ecosystem. The fear they bring along may be the very angle that helps save them from dying out.

    Ray Tokuda, a 54-year-old Japanese American, is proud of the title his school has given him. He is a Shifu, a Chinese word literally meaning a master, mentor or senior practioner of martial arts.

    Tokuda has reason to be proud. He has been involved with Chinese martial arts for almost four decades. After learning them at the martial arts school in New Mexico State, today he is among the most experienced kung fu teachers of the school.

    Practicing martial arts two to three hours and helping students improve their skills have become Tokuda's daily routine. He expects to practice and teach martial arts for the rest of his life. "I'm still learning. It's worth more than a lifetime to learn Chinese martial arts," he said." Once I started, I just couldn't stop. I think it's also the magic of Chinese culture."

    Tokuda was sent to the martial arts school when he was 10. He still remembers how unwilling he was when starting out." My father had always wanted to learn Chinese martial arts but never got the chance, so he put his kid in," he said. "I was so afraid at that time because I thought kung fu was all about fighting."

    But things changed after he learned that martial arts were more than punching and kicking.

    "One of the things martial arts teach me is overcoming adversity," Tokuda said. "As a little kid, my first lesson was like, oh, look, this is a thing that I can get through by diligence, perseverance(毅力)and dedication, and that was priceless for my life."

    Learning Chinese martial arts opened a gateway for him to better understand Chinese culture because he could hear a lot of ancient Chinese kung fu-related stories. "It is like in America, where we hear stories about knights in shining armor and King Arthur and noble deeds done," he said. "I feel martial arts preserve something of ancient China that can't be found in books. They are sort of an oral history."

    Tokuda has also been invited to various events in his home state to showcase traditional Chinese culture, including the dragon dance and lion dance, which he also learnt at the martial arts school. Because of this, he is now considered a cultural envoy (使者) in the eyes of the public.

    Robots are increasingly being developed to think and act like humans. But it is difficult for engineers to create humor (幽默) in machines. Computer scientists have hoped to help them understand humor. But they failed again and again. Why is it so difficult?

    Kiki, a computer language expert (专家), studies humor at a university. "Most robots are powered by artificial intelligence (人工智能AI). But AI will never understand jokes like humans do." He said, "The main problem is that AI system doesn't have the sense of humor."

    Other experts agree that context (语境) is very important to understand humor, both for humans and robots. In one project, Tristan Miller, a computer scientist, studied more than 10, 000 puns. Puns are a kind of joke that uses a word with two meanings. For example, you could say, "Balloons (气球) do not like pop music." The word "pop" can be a way of saying popular music, or "pop" can be the sound a balloon makes when it explodes(爆炸). "A robot might not understand the joke because it doesn't know the meaning of the puns." Miller said.

    Although it's difficult, some scientists say there are good reasons to keep trying to teach humor to robots. It can make machines understand humans better and serve humans better. And it can also help them to think more like humans.

    But other scientists don't think it's a good idea to teach humor to robots. They may find humor, but they may use it in a wrong way. Maybe bad Al will start killing people because it thinks it is funny. Besides, it may make some people feel not safe. The comedians(喜剧演员) may lose their jobs when the robots can understand humor.

    The Huaqing Palace Heritage Site

    Address: At the foot of Lishan Mountain in Lintong, 30 kilometers east of Xi'an.

    Opening hours: From March to November: 7:00-18:00;

    From December to February: 7:30-18:30.

    Bus routes: 914, 915, U5, and 306.

More than 400 athletes across a variety of sports, ages and levels of experience were questioned for the study by sports psychology experts from Staffordshire University and Manchester Metropolitan University. The findings reveal that athletes' belief systems—specifically irrational（非理性） beliefs—are related to poorer self-confidence, and in turn, greater competitive anxiety and depressive symptoms.

"Phrases that reflect self-depreciating（贬低） beliefs such as 'If I lose, I'm a failure' or 'If I face setbacks, it shows how stupid I am' are warning signs," said the authors. Paul Mansell, Lecturer in Sport and Exercise Psychology at Staffordshire University, said, "Despite the psychological benefits of physical activity, studies frequently report poor mental health in athletes, which may be exacerbated by adversities, such as injury, de-selection, and performance pressure. We investigated athletes' beliefs, how they view stress, their levels of self-confidence and put all this data together to work out what might predict psychological well-being. We found irrational beliefs to be a core reason for symptoms of poor mental health in athletes."

This is the first known study that has examined irrational beliefs, self-confidence, and the psychological well-being of athletes all together. Irrational beliefs are extreme, rigid, and illogical ideas that people hold. For example, a person might believe that they "must" get what they want, or that just because they have failed, they are a "complete failure".

"We can all work to help athletes develop mindsets that help them deal with the challenges of sport and life. By encouraging rational and logical beliefs about performance, we can help athletes to stay healthy amidst the high demands of competitive sport," said Paul Mansell.

The author s propose Rational Emotive Behavior Therapy(REBT) as an effective tool for protecting self-confidence. REBT helps athletes to challenge these self-depreciating beliefs and develop beliefs that are more helpful and healthy. For example, rather than believe "I am a failure if I fail", this might be countered with "Failing is not ideal, but it does not mean that I am a failure".