Apple is to open a research lab in the southern Chinese city of Shenzhen, according to Tim Cook, its chief executive, as it seeks to boost sales in the country and improve ties with the authorities.

    Beijing has been encouraging foreign technology companies to carry out more high-end work on the mainland as part of efforts to revitalize local industry.

    It will be Apple's second facility in China. It already has a new research and development facility in Beijing.

    The two R&D centers were “aimed at strengthening relationships with local partners and universities as we work to support talent development across the country”, Apple said in a statement.

    A closer relationship with the Chinese authorities has been a priority following setbacks for the US technology company this year.

    The iPhone has been losing market share to high-end handsets made by local competitors including Huawei, Vivo and Oppo, which topped the rankings in the second quarter, while Apple languished in fifth place, according to Canalys data.

    Analysts said the announcement of the R&D centre was Mr. Cook's latest attempt to gain favour with Beijing, following the US group's $1billion investment in Didi Chuxing, the Chinese car-hailing company, in May.

    Apple has had to change its approach in China as it faces rising nationalism and high-quality local competition, according to Ge Jia, a tech blogger, who wrote yesterday: “It's time for Apple to cast aside their pride.” “Their previous strategy of only selling devices to China without leaving anything behind is not working any more and they are starting their process of localisation in China through the Shenzhen lab.”

    Most people know precious gemstones (宝石) by their appearances. An emerald flashes deep green, a ruby seems to hold a red fire inside, and a diamond shines like a star. It's more difficult to tell where the gem was mined, since a diamond from Australia or Arkansas may appear the same to one from the Democratic Republic of the Congo. However, recently, a team of scientists has found a way to identify a gemstone's origin.

    Beneath the surface of a gemstone, on the tiny level of atoms and molecules（分子）, lie clues (线索) to its origin. At this year's meeting of the Geological Society of America in Minneapolis, Catherine McManus reported on a technique that uses lasers (激光) to clarify these clues and identify a stone's homeland. McManus directs scientific research at Materialytics, in Killeen, Texas. The company is developing the technique. “With enough data, we could identify which country, which mining place, even the individual mine a gemstone comes from,” McManus told Science News.

    Some gemstones, including many diamonds, come from war-torn countries. Sales of those “blood minerals” may encourage violent civil wars where innocent people are injured or killed. In an effort to reduce the trade in blood minerals, the U.S. government passed law in July 2010 that requires companies that sell gemstones to determine the origins of their stones.

    To figure out where gemstones come from, McManus and her team focus a powerful laser on a small sample of the gemstone. The technique is called laser-induced breakdown spectroscopy. Just as heat can turn ice into water or water into steam, energy from the laser changes the state of matter of the stone. The laser changes a miniscule part of the gemstone into plasma, a gas state of matter in which tiny particles（微粒）called electrons separate from atoms.

    The plasma, which is superhot, produces a light pattern. (The science of analyzing this kind of light pattern is called spectroscopy.) Different elements produce different patterns, but McManus and her team say that gemstones from the same area produce similar patterns. Materialytics has already collected patterns from thousands of gemstones, including more than 200 from diamonds. They can compare the light pattern from an unknown gemstone to patterns they do know and look for a match. The light pattern acts like a signature, telling the researchers the origin of the gemstone.

    In a small test, the laser technique correctly identified the origins of 95 out of every 100 diamonds. For gemstones like emeralds and rubies, the technique proved successful for 98 out of every 100 stones. The scientists need to collect and analyze more samples, including those from war-torn countries, before the tool is ready for commercial use.

    Scientists like Barbara Dutrow, a mineralogist from Louisiana State University in Baton Rouge, find the technique exciting. “This is a basic new tool that could provide a better fingerprint of a material from a particular locality,” she told Science News.

    Antiquities are ancient objects and artworks. Museums acquire works to display from many different sources. Sometimes they purchase them. Other times they receive donations. Today there are strict rules forbidding art that has been stolen from other countries. However, antiquities that have been at museums for decades or even centuries may have arrived there by questionable means. Now, some countries claim that museums have a responsibility to return these antiquities to their original locations.

    There are many examples of this debate. Perhaps the most famous is the argument between Greece and the UK over the Elgin marbles. In the early 19th century, the Earl (伯爵) of Elgin had numerous sculptures taken from Greece to the UK. When Elgin did this, Greece was still a part of the Ottoman Empire. He claimed that he had received a permit to export the sculptures. Today the marbles are on display in the British Museum^ However, Greece wants them to be returned to their original location.

    Should museums return these antiquities? Experts disagree. Malcolm Bell III says yes. Bell is a retired professor of art at the University of Virginia. He says, “Many antiquities and artworks have special cultural value for a particular community or nation. When these works are removed from their original cultural setting they lose their context and the culture loses a part of its history.”

    According to Bell, a country's request for the return of an antiquity “usually has a strong legal basis.” It “was exported illegally, and is now stolen property.” He called the return of antiquities “an expression of justice.”

    James Cuno says not always. Cuno is president of an art museum in Los Angeles. He is also the author of the book Who Owns Antiquity?. Cuno agrees that museums have “a social and legal responsibility” to return illegally exported antiquities. However, he doesn't support the return of legally acquired works.

    “An area of land held today by a given nation-state in the past likely belonged to a different political entity (实体). Even if one wanted to reunite scattered works of art, where would one do so? Which among the many countries, cities, and museums in possession of parts of a work of art should be the chosen 'home' of the reunited work?” Cuno believes that museums should collect art from the world's diverse cultures. This should be done “through purchase or long-term loan and working in cooperation with museums and nations around the world.”

    This debate is far from over. As a complex question with no easy answer, the issue requires more study.

    Last year, Claire Noble-Randall woke up at 5:30 am every morning. She had to catch two buses to arrive in time for first-period chemistry at Ingraham High School in Seattle, US.

    Ingraham starts at 8 am, but Noble-Randall often didn't go to sleep until after midnight. “It was really hard not to fall asleep in class,” she said.

Her mom solved the problem this year when she discovered that other parents had hired a private city tour bus to take their children to the school.

    “Now, she leaves the house at a much more reasonable time 7:10 in the morning…to catch the little tour bug at 7:23 am,” said her mother, Noelle Noble.

    That may be one way to help students get more sleep. But more than 3,300 people have signed an online petition (请愿) looking for a better solution from the Seattle school district. Those who have signed the petition want all high schools and middle schools to start no earlier than 8:30 am. Most of Seattle's high schools and middle schools start at 8 am or earlier.

    Later start times for teenagers is an idea that some parents around the nation, have wanted for years. They've provided plenty of scientific evidence that teenagers tend to be night owls and delayed start times improve their health, mood, attention, and, in some cases, learning.

    But attempts to delay start times for teenagers haven't worked. Coaches don't want late dismissals (放学) cutting into sports practices; community groups don't want to wait longer for gyms and fields and before- and after-school programs don't want to change their schedules.

    This time, however, they've got Seattle School Board. President Sharon Peaslee on their side. She herself is the mother of two high school students. Peaslee hopes other board members will pass her plan calling on the district to find a way to make the changes.

    I had about 10 minutes to exercise before I had to pick up my two older daughters from school yesterday. It was a busier day than usual for me with a couple of meetings besides my regular work.

    Years ago, I would have put off my workout and would have left things for the next day. But since it was a busy day as well, I knew that I may not have all that much time either. So, I picked up my kettle-bell (哑铃) and went to town for 4 minutes.

    See, 4 minutes, if that's all you've got, is enough to give your body a great fat-burning exercise. How did I get a killer workout in 4 minutes? I used a training workout discovered 10 years ago by a Japanese Sports Scientist called a TABATA.

    It includes 20-second periods of warm-up, followed by 10-second periods of rest and 4-minute straight exercise. How is a 4-minute exercise able to burn fat? It all depends on the quality of work you do. Not on the quantity. Here's how I did it yesterday.

    You should never forget your warm-up. A TABATA workout is 20 seconds of 2-arm Kettle-bell swings, 10 seconds rest, 20 seconds push-ups, and 10 seconds rest. You should do those 4 rounds. That's it. I was done in a total time of 8 minutes by the time and when I got to school my heart was still pumping pretty hard.

    A healthy body is needed for studying and working, and efficiency (效率) is the key to building a great body in the least amount (数量) of time possible and you can't get more efficient than a 4-minute workout.

There are thousands of puzzles to choose from for you, such as jigsaw puzzles, puzzle books and more. They all have something in common: they test your skills or knowledge. Here are four of the most common:

Word puzzles

One of the most popular word puzzles — the crossword. It can be done with paper and pencil or online. Sometimes word puzzles involve finding new words within a large group of letters. This type of word puzzle is called a word search.

Word puzzles usually test your vocabulary. Knowing the language that the game is designed in is required for success, however.

Mechanical puzzles

Mechanical puzzles have pieces that must be arranged in some way. The world's best-selling puzzle, the Rubik's Cube, is a mechanical puzzle. As of 2020, over 450 million Rubik's Cubes had been sold.

Jigsaw puzzles also fall into this category. They typically involve putting pieces in the right place to form a picture. Jigsaw puzzles have from two to over 550,000 pieces — the largest one on record.

Logic puzzles

Figuring out the solution to a logic puzzle requires careful thought rather than guessing. Sudoku and Mine Finder are examples of logic puzzles. In Mine Finder players must determine where the mines are hidden in a grid.

Math puzzles

Math puzzles involve numbers, words or objects and the use of math. Surprisingly, the ever-popular Candy Crush is classified as a math puzzle. Math skills are required for players to successfully move and match colored candies.

There are many other kinds of puzzles. But no matter which you prefer, puzzles are a great way to entertain.