As global temperatures continue to rise, more “extreme rain” events—intense, cats-and-dogs down pours—can be expected, said the study, published Monday in the journal Nature Climate Change. And that, scientists said, means an increased flood risk, particularly for the world's driest areas. The study challenges the idea that global warming is causing dry areas to become drier and wet areas wetter.

    “In both wet and dry regions, we see these great increases in heavy precipitation（冰雹）,” lead author Markus Donat, a climate scientist at the University of New South Wales, told Nature.

    Donat and his team collected data from 1951 to 2010 on extreme precipitation events from 11, 000 weather stations around the world, Nature reported.

     In that time, the number of days with“extreme precipitation” increased 1 percent to 2 percent per decade.

  “We found a strong relationship between global warming and an increase in rainfall, particularly in areas outside of the tropics,” Donat said in a statement.

  “Importantly, this research suggests we will see these extreme rainfall events increases at regional levels in dry areas, not just as an average across the globe,” Donat added.

    Peter Stott, a senior climate scientistat Met Office, told Climate Central that the study's findings are important, because more violent rainfall and flooding will “challenge our capability toadapt to a rapidly changing climate.”

    As Nature reported, the researchaligns（结盟）with a 2015 study that found global warming has led to a sharp increase in record-breaking precipitation events. Donat told Nature that his study should come as a warning to world governments.

    Two students started quarreling at school. One student shouted dirty words at the other, and a fight began. What can be done to stop fights like this at school? In some schools, the disputants sit down with peer mediators(同龄调解者). Peer mediators are students with special training in this kind of problems.

    Peer mediators help the disputants to talk in a friendly way. Here are some of the ways they use:

1) Put what you think clearly but don't say anything to hurt the other. Begin with “I feel…” instead of “You always…”

2) Listen carefully to what the other person is saying. Don't stop the other person's words.

3) Keep looking at the other person's eyes when he or she talks.

4) Try to see the other person's side of the problem.

5) Never put anyone down. Saying things like “You are foolish” makes the talk difficult. 6) Try to find a result that makes both people happy.

    Peer mediators never decide the result or the winner. They don't decide who is right and who is wrong. Instead, they help the two students to find their own “win-win” result.

    Mark Twain, the famous American writer and a great master of humor, liked to play jokes on others. But once a joke was played on him. One day Mark Twain was invited to give a talk in a small town. At lunch he met a young man, one of his friends.

    The young man said that he had an uncle with him. He told Mark Twain that his uncle never laughed or smiled, and that nobody and nothing was able to make his uncle smile or laugh.

    "You bring your uncle to my talk this evening," said Mark Twain. "I'm sure I can make him laugh."

    That evening the young man and his uncle sat in the front. Mark Twain began to speak. He told several funny stories and made everyone in the room laugh. But the man never even smiled. Mark Twain told more funny stories, but the old man still kept quiet. Mark Twain continued to tell his funny stories. Finally he stopped. He was tired and quite disappointed.

    Some days later, Mark Twain told another friend what had happened." Oh," said his friend, "I know that man. He's been deaf for years."

    Here's a selection of festivals for tourists to the United States in summer.

    San Francisco Silent Film Festival

    Films at this odd cinematic event have a variety of musical accompaniments,including piano and violin.It includes some classic silent movies.If you want to see them all,you can buy a festival pass.

    May 29 to June 1; www.silentfilm.org

    Union Street Festival

    This popular street fair stretches out over six blocks of the city,in the fashionable shopping area of Union Street.This year,there's beer,wine tasting and more separate themes—fashion,cuisine,tech,local,craft,and health and fitness.

    June 7 to 10; www.unionstreefestival.com 

    North Beach Festival

    This is San Francisco's oldest street party,with live entertainment,delicious food and arts and crafts.Situated in the Little Italy district,known for its associations with the "Beat Generation",festival goers are guaranteed plenty of good Italian food.There is also as the “blessing of the animals”,a San Francisco tradition which takes place at the National Shrine of Saint Francis of Assisi (610 Vallejo Street) at 2 pm on both days of the festival.

    June 14 to 16; www.sfnorthbeach.org

    Stern Grove Festival

    This is the oldest free summer arts festival of its kind in the United States.It includes a wide variety of acts,from the local symphony orchestra to well known artists such as Smokey Robinson.

    Sundays from June 22 to Aug 24; www.sterngrove.org

    The English language has a lot of words which can be used in many different ways and in many different experiences.

    One such example is the word matter. In fact, matter can mean just about anything. It could be one of the most useful words in the English language.

Let's get to the heart of the matter —- a matter of principle(原则).

    If someone says that you owe(欠) him $50, but you don't, a friend might say, "Well, you could pay him the $50. It's not that much money. Then you won't have to hear him say it anymore." But if you do not owe him the money, do not pay him the money. It's a matter of principle.

    There is another way to use the word matter. But be careful with your choices of words.

    If you ask someone, "What's the matter?", it shows you are worried about the other person. But saying, "What's the matter with you?" has a completely different meaning. And it usually sounds rude. In fact, when you say, "What's the matter with you?", you are suggesting that the person did something wrong or stupid.

    Another expression that could sound rude is to say, "It doesn't matter to me." Here, it depends on the context, and how you say it.

    Let's say you tell someone that a friend just got a big raise at work. That person answers with, "It doesn't matter to me." Here, it means he or she does not care. And it sounds rude.

    But saying, "Oh, you pick where we eat dinner. It doesn't matter to me." does not sound rude. In the situation, "it doesn't matter" shows you are easy-going.

    No matter how you look at it and what you say, matter is a very useful word. And it's only a matter of time before you will become an expert on the use of matter.

A kind of blue dye (颜料) called folium had been widely used to paint pictures on the pages of manuscripts (手稿) created in the Middle Ages. But long ago, this watercolor fell out of use.

"Manuscripts are an important part of the cultural works of art in the Middle Ages," said scientist Maria in an email to CNN. "Color is a basic feature of these manuscripts. To let ancient manuscripts. keep a good condition for future generations, we sometimes need to repaint their inside pictures through the ancient dye — like folium — that was once used in these manuscripts. But everyone who knew how to prepare folium had died long ago. So 'I led a team to study this dye."

Her team turned to books from the 1400s and found one that described the plant that was its source. It is a tiny plant with silvery-green leaves. Days later, the scientists reached a village in south Portugal, where nobody knew this little plant. However, after carefully going through a plenty of different plants growing there, the scientists finally raked out the plant they wanted and brought some back to their laboratory.

Back in the lab, the scientists produced the dye with the help of an ancient text on colors. The text has clearly described the ways to make it. "It's cool to have done that work of looking in the historical records and traveling back in time," says Casadio, who was not part of this study. It recreates an ancient process. By making the dye, the scientists could study its chemistry without experimenting on priceless delicate (易损的)  works of art, she points out.

Now, the researchers don't know the dye's stability(稳定性)and its ability against the environment that may wear and break it down over time. "To know such information is necessary if we desire to make these colors last long enough," Maria said. "So our study will continue."