Houses fall down. Trees fall over. Large holes form in the ground. Could Alaska be sinking? That's what some villagers in Alaska have been asking themselves recently and scientists think they know why. Warmer temperatures may be causing Alaska's frozen ground to thaw (解冻).

    About 85 percent of Alaska's land surface has permafrost (永久冻结带). Permafrost supports the ground above it—including trees, houses, and roads. But why is the permafrost thawing?

    Some scientists say that human-caused pollution is leading to global warming. And most scientists agree that Alaska has been getting warmer. They say that the warmer temperature is causing permafrost to thaw in some areas. The thawing permafrost can cause problems for people, plants, and animals.

    The collapsing (倒塌) is a problem in the villages in Alaska which are built on permafrost, and some of them may have to move to safer ground, where there is no permafrost.

    The Alaskan town of Glennallen saw its old post office collapse. And, according to James Walters, a permafrost expert at the University of Northern Iowa, house-moving companies have been very busy.

    “Melting permafrost can also destroy trees and forests,” Walters said. “When holes in the ground form, trees fall into them and die. This could turn a forest into a swamp (沼泽), and animals which need the forests will have to move elsewhere.”

    “The melting could cause severe problems.” Walters says, “This could take hundreds of years, but in the end Alaska will look quite different from what it looks like now.”

    Younger students experience school bullying (欺凌) more frequently than older ones, and male students are bullied more than their female peers, a survey found.

    It also found that nearly half of the students had been intentionally hit or knocked down by classmates. About 6 percent said they are targeted by bullies on campus every day. The survey also found that students from ordinary schools experienced more bullying than peers from key institutions, and children from poor families are more likely to be bullied at school.

    Being bullied can have a negative impact on a child's personal development and academic performance, according to Zhou Jinyan, a researcher who led the study at Beijing Normal University. 揅hildren being bullied will find it hard to trust others,? Zhou said. 揟hey may often feel anxiety, anger, resentment or depression. These emotions will further undermine their ability to control their own life.”

    In recent years, bullying on Chinese campuses has been frequently reported and has attracted widespread attention and concern. The most recent incident to arouse heated discussions took place in December at Beijing's Zhongguancun No.2 Primary School. A fourth-grade student was bullied and laughed at by classmates, causing him acute stress disorder.

    The Supreme People's Procuratorate (最高人民检察院) received about 1,900 cases related to school bullying in 2016. Meanwhile, there was a notable increase in bullying reports involving middle school students from 14 to 18 years old.

    Zhou came up with some ways to solve the problem, including boosting communication between teachers, parents and students and trying to establish more harmonious relationships among children. She said it was strongly suggested that parents try to be involved in their children's educational experience, as their presence and companionship have proved effective in reducing bullying and its negative effects.

    Hadi Partovi, founder of Code.org believes every student should learn the basics of computer science just like they do math, physics, or biology, regardless of what they want to do in the future. The expert says knowledge about the subject is important to understand how the world around us works and compares it to learning about photosynthesis(光合作用), even though not every student is going to be a botanist. To spark students' interest, he created the “Hour of Code,” which introduces the world of computing to anyone, from ages 14 to 104, in a fun, interactive manner. Observed annually during Computer Science Week, the event now draws tens of millions of kids from over 180 countries.

    The “Hour of Code”, which can be scheduled anytime during Computer Science Week, begins with an introductory video on computer science. Participants can then select from hundreds of fun assignments that are sorted by both grade level and coding experience. Though each project is designed to last just sixty minutes, beginners can deal with as many challenges as they desire.

    To help introduce computer science in classrooms on a more regular basis, Code.org has also developed a catalog of online courses that can be incorporated(纳入)in a school's regular curriculum. Since the nonprofit began offering the courses in 2013, over 704, 000 teachers have signed up to teach introductory computer science to over 22 million students worldwide.

    Thanks to the efforts of the pioneer, about 40 percent of US schools now offer computer science as a subject. The numbers are even higher—an impressive 70 percent—if after-school offerings such as robotics clubs are included. Even more encouraging, eight years ago, just 19, 390 students took an Advanced Placement Computer Science exam. By the spring of 2017, the number had jumped 415 percent to 99, 868.

    If you want to disturb the car industry, you'd better have a few billion dollars: Mom-and-pop carmakers are unlikely to beat the biggest car companies. But in agriculture, small farmers can get the best of the major players. By connecting directly with customers, and by responding quickly to changes in the markets as well as in the ecosystems(生态系统), small farmers can keep one step ahead of the big guys. As the co-founder of the National Young Farmers Coalition (NYFC, 美国青年农会) and a family farmer myself, I have a front-row seat to the innovations among small farmers that are transforming the industry.

    For example, take the Quick Cut Greens Harvester, a tool developed just a couple of years ago by a young farmer, Jonathan Dysinger, in Tennessee, with a small loan from a local Slow Money group. It enables small-scale farmers to harvest 175 pounds of green vegetables per hour—a huge improvement over harvesting just a few dozen pounds by hand—suddenly making it possible for the little guys to compete with large farms of California. Before the tool came out, small farmers couldn't touch the price per pound offered by California farms. But now, with the combination of a better price point and a generally fresher product, they can stay in business.

    The sustainable success of small farmers, though, won't happen without fundamental changes to the industry. One crucial factor is secure access to land. Competition from investors, developers, and established large farmers makes owning one's own land unattainable for many new farmers. From 2004 to 2013, agricultural land values doubled, and they continue to rise in many regions.

    Another challenge for more than a million of the most qualified farm workers and managers is a non-existent path to citizenship — the greatest barrier to building a farm of their own. With farmers over the age of 65 outnumbering(多于) farmers younger than 35 by six to one, and with two-thirds of the nation's farmland in need of a new farmer, we must clear the path for talented people willing to grow the nation's food.

    There are solutions that could light a path toward a more sustainable and fair farm economy, but farmers can't clumsily put them together before us. We at the NYFC need broad support as we urge Congress to increase farmland conservation, as we push for immigration reform, and as we seek policies that will ensure the success of a diverse and ambitious next generation of farmers from all backgrounds. With a new farm bill to be debated in Congress, consumers must take a stand with young farmers.

    While most people have the idea that volcano eruptions are one of the most destructive disasters in nature, seeing a volcano erupt is a wonderful experience, and you can really feel the heat by climbing to the summit of Pacaya for a close-up view.

    There are guided tours every day up this highly active volcano from Antigua, giving travelers a chance to see Mother Nature at her most powerful. Pacaya is an easy drive from Antigua, a beautiful city with many colorful houses along its old streets that are turned into art-works during its Holy Week festival. No matter when you come to Antigua, you won't miss the Pacaya-tour companies.

    But climbing Pacaya is no easy job: it is 2,560 meters high, and reaching the summit takes two to three hours of seemingly one-step-forward and two-step-back movements. As you climb you hear the dull sounds of eruptions high above. Steaming, hot remains from recent eruptions begin to line the path as you near the active summit: the Mckenney Cone (火山锥). Just as though you were going to walk over to the edge of the cone, the road turns to the left and up to the relative safety of the old, inactive summit.

    Many tours are timed so that you arrive at the cone of the volcano in plenty of time for sunset and the full contrast between the erupting red lava(岩浆) and the darkening sky. On a good day the view from the summit is extremely exciting. The active mouth boils, sending red lava over its sides, and once in a while shoots hot steams up to 100 meters into the air. There is a strong bad smell in the air even if you take care to be upwind of the cone. As evening turns deeper into the night, the burning lava quietly falls down the side of the volcano. For you, too, it is time to get down.

The Feynman Technique(费曼学习法)is a powerful method that you can use to learn anything faster because it forces you to actively think about the problem instead of passively reading or listening to someone else talk about it. You can take the following five simple steps to study better.

·Find out the topic you want to learn. {#blank#}1{#/blank#} Otherwise, you'll end up jumping between topics without developing a deeper understanding of any of them.

·Explain the topic as if teaching a sixth-grader. This step is the heart of the FeynmanTechnique—{#blank#}2{#/blank#}.This requires you to meet the child at their level of understanding by using the simplest way.

.Identify areas of improvement in your explanation. You'll need to critically(批判性地)review the explanation you cane up with in Step Two {#blank#}3{#/blank#}. Try to find any knowledge gaps, together with any areas where you felt that you couldn't explain the topic simply.

·Improve and optimiez(优化) your explanation. Think about all the knowledge gaps and otherareas of improvement you found before. {#blank#}4{#/blank#}

· Repeat the steps until you've achieved mastery of the topic. Keep going through each step you're fully satisfied with your explanation.{#blank#}5{#/blank#}, and that is why going through all the prior snnjust once is usually not enough to achieve topic mastery.

A. Use those to improve your explanation

B. To do so, take a critical look at your explanation

C. Make sure that your explanation is interest-based

D. Your explanations need to be short and to the point

E. The Feynman Technique works best with a repeat

F. It's important that you clearly know the topics you're trying to learn

G. Explaining the topic simply enough to be understood by a sixth-grade student