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A tiny crack grew in a very small piece of metal when placed under repetitive stretching. The experiment, designed to study crack growth, continued as predicted for a while. But then, something unexpected happened. The crack stopped growing and instead began to get shorter, effectively "healing（愈合）"itself. This incredible observation was made by a group of researchers at Sandia National Laboratories. The findings were recently published in the journal Nature.

It would be reasonable to think, prior to this discovery, that self-healing metal was something that could only be found in science fiction. However, Dr. Michael Demkowicz, a professor in Texas A&M University's materials science and engineering department and co-author of the recent study, held no such assumptions.

Ten years ago, while an assistant professor at Massachusetts Institute of Technology's materials science and engineering department, Demkowicz and his student predicted self-healing in metals. "We didn't set out to find healing. My student, Guoxiang Xu, was doing experiments on fracture（断裂）," Demkowicz said. "We accidentally observed healing in one of his experiments and decided to follow up." Then, just like now, the results in 2013 were surprising.

Both the 2013 models and the recent experiment used nanocrystalline（纳米晶体）metals, which make studying self-healing easier because their small grain size allows for more microstructural features that even small cracks can interact with. Demkowicz said that these features are common in many metals. One condition common to both the 2013 theory and the recent experiment is that both were conducted in vacuum environments without foreign matter. Such outside matter could influence crack surfaces' ability to bond back together.

Even with this limitation, applications could still be possible for space faring technology or internal cracks that are not exposed to outside air. "The main impact of the current work is to move the original theoretical prediction off the drawing board and show that it occurs in reality," Demkowic z said. Potential applications of this work could vary widely. Demkowicz suggests that self-healing could be possible in conventional metals with larger grain sizes, but future investigations will be needed.

A recent study published in the Journal of the American Chemical Society suggests that Leonardo da Vinci was more experimental with his well-known "Mona Lisa" than previously thought—and was likely the creator of a technique seen in works used a century later.

A team of scientists in France and Britain has detected a rare mineral compound（矿物化合物）, plumbonacrite, within the piece. Plumbonacrite forms when lead oxides（铅氧化物）combine with oil. Mixing these two substances is the technique that later artists like Rembrandt used to help the paint dry, according to the study.

Detecting the rare compound in the "Mona Lisa" suggested that Leonardo could have been the original user of this approach, said Gilles Wallez, an author of the study. "Everything that comes from Leonardo is very interesting, because he had lots of ideas, and he was an experimenter, attempting to improve the knowledge of his time," Wallez said. "Each time you discovered something in his processes, you discovered that he was clearly ahead of his time."

The "Mona Lisa", like many other paintings from the 16th century, was created on a piece of wood that required a thick base layer. The researchers believed that Leonardo had made his mixture of lead oxide powder with linseed oil to produce the thick coat of paint needed for the first layer, while unknowingly creating the rare compound.

Nowadays, researchers aren't allowed to take samples from the masterpiece, which resides at the Louvre in Paris and is protected behind glass. Using a microsample that had been taken from an area of the artwork just behind the frame, however, scientists were able to analyze the paint by using a high-tech machine. "These samples have a very high cultural value," Wallez said. "You can't afford to take big samples on a painting."

On Sunday night, the police found a baby koala in a bag in the town of Wishart in Queensland, Australia, during a traffic stop. Queensland police spokesperson Michael Beatty said that the officers asked a 50-year-old driver if she had anything to report. She then told the officers that she had a baby koala in her bag.

"Not quite believing their ears, the officers cautiously opened the bag and found this lovely boy and we've called him Alfred," the spokesperson said. "The young koala is about 6 months old and weighs 1.5 kg. It appears to be healthy, though it was very thirsty."

The police are warning people who find koalas to turn them over to authorities, rather than try to take care of them themselves. Koalas are protected in parts of Australia, including in Queensland, where they have been listed as "threatened" under the Nature Conservation Act.

Of course, koalas are also violent animals. One particularly wild koala even attacked a farmer in South Australia when she was riding along a muddy road.

"As it started running towards me, I thought I'd better speed up," the terrified farmer told reporters. "But the road was too muddy, So I abandoned my bike and ran away. Fortunately, it ran up and attached itself to the dirty wheel—perhaps mistaking it for a eucalyptus tree."

Deakin University biologist Desley. Whisson has some tips in case you experience this    predicament. "Koalas more generally run from than to people. The farmer did the right thing by moving away from her bike," she said. "The best advice I can give to people is to not fight with a koala displaying unusual behaviour. Make sure that there is another object between you and the koala so that it can't climb you. Or you can just simply run. Their fingers are very sharp."

She also believed the koala might have been confusing the sound of the bike with that of a koala mate.

Fun Fall Weekend Getaways.

Gulf Shores, Alabama: 

Alabama's Gulf Shores is attractive year-round, but the fall months bring fewer crowds and more affordable prices on hotels. Head to Gulf Shores for warm ocean waters and lovely white sand beaches that you may have all to yourself. There's also plenty to do at this beach destination outside of playing in the sand and surfing. For example, you can visit a downtown music bar.

Albuquerque, New Mexico

Albuquerque's amazing landscapes provide an enjoyment for visitors year-round. However, visiting in fall allows you to enjoy the famous Albuquerque International Balloon Fiesta, which takes place in October. Book a trip in early October to see hundreds of brightly colored balloons dot the sky—you can even take a balloon ride yourself. Because this hot air ball oon festival is such a popular event, you'll want to secure accommodations well in advance.

Laconia, New Hampshire

You may not have heard of Laconia before. This small New Hampshire city is mostly known for its incredible fall festivals. Perhaps you've heard the famous New Hampshire Pumpkin Festival, which takes place here in late October. Plan a weekend getaway to check out the amazing display of jack-o'-lanterns, live music, the Children's Costume Parade, a cornhole tournament and more.

Shenandoah National Park, Virginia

Located around 75 miles southwest of the nation's capital is Shenandoah National Park, a great place for leaf peeping（赏叶）and exploring the outdoors in autumn. This national park has more than 200,000 acres of forest, waterfalls, flower fields and plenty of wildlife. For example, you can spot black bears, deer and birds throughout the national park.

I was a bad boy in a village in India. At least I was labeled that way because I had no interest in school or studies. I used bad language, hung around with other "bad" boys, skipped school and ran through the fields. No one thought I would do anything worthwhile with my life. And I'd heard many people in our village talking. "Why bother going to school? These kids end up back on the farms anyway. He'll never amount to anything." My parents and teachers were disappointed with my average marks.

My mother envisioned a different future and knew the value of education to create a better life. By the time I entered the 12th grade, I had taken a good look at myself and realized the life I was creating. The bad boy image troubled me. I didn't believe I was a bad boy. I didn't want to be a bad boy. These realizations forced me to acknowledge that my mother was right—education was my only way out. I worked hard to finish my high school, and then I decided to apply for higher education in university. But this village bad boy faced too many challenges.

Firstly, my family had very limited money. In addition to that, my grades were not good. There was very little chance I'd gain admission to a university. Still, I took a chance and applied. The last day of admissions, I visited the university to check my result. I looked down the list, and there it was, "Parashram J. Patil". Finally, I'd been admitted. Now, it was the last day to pay, so I had to find money to cover my fees.

注意：1.续写词数应为150左右；2.请按如下格式在答题卡的相应位置作答。

注意：1.词数80左右；2.请按如下格式在答题卡的相应位置作答。