How long has 3-D technology been around? Most of us might think of crowds of teenagers in a 1950's movie house watching Bwana Devil in 3-D. But 3-D technology made its first appearance on the scene in 1838 with the first stereoscope(体视镜). And the first actual 3-D movie was a 1903 film called Le Ariveed'un Train.

    Although it has such a long history, the technology has still remained based on one simple principle—to make 3-D effects you must find a way to project two slightly different pictures to each eye. Modern 3-D technology works by rapidly flickering(闪动)two versions of the movie and projecting them onto each eye. The brain does the rest of the work, combining the two pictures together into one and giving the show the appearance of depth, the third dimension.

    But does this exposure, especially long exposures, cause harm to the child's developing brain and visual system? Unfortunately, long-term studies on new flicker digital 3-D technology and children aren't yet available. We do not know if regular or daily 3-D viewing over years affects the developing visual system, although older 3-D methods basically do the same thing and are not considered harmful.

    The question of possible harm in modern 3-D use in TV is really based on two facts: the amount of time children will now be watching 3-D TV each day and the sensitivity some children show in reaction to 3-D viewing. It is difficult to make actual lab studies of longer term 3-D viewing in children because of the possible harm of the experiment. Researchers will have to wait until 3-D TV technology is already in the marketplace for a number of years, then check heavy 3-D TV watchers and compare them with non-watchers.

    With a 3-D television technology in the home, we will soon be able to answer the question of whether or not longer and more frequent periods of 3-D exposure cause more changes in the visual system. We may find that the bigger problem is the introduction of a new technology that leads to even more time spent on TV rather than playing outdoors.

    While visiting the North pole in winter may not be at the top of your bucket list, the ever-changing ICEHOTEL, which opened its doors to visitors on December 14 this year, may change your mind.200 km north of the Arctic Circle in the Swedish village of Jukkasjārvi, the hotel, which is carved entirely from ice, is rebuilt annually.

    The 35 rooms, built to accommodate visitors on all kinds of budgets, vary from expensive suites to basic rooms that are furnished with just an icy bed and a reindeer skin. Among the highlights this year is the “Spruce Woods” suite. Sculpted by Christopher Pascoe and Jennie O'Keefe of Canada, it describes a camping scene complete with a classic microbus, a forest, and even an artificial campfire.

    There is also the artfully-carved “Living Ocean” suite to remind visitors of the importance of saving our oceans. The room is full of carved sea life that includes coral and a shark “swimming” right over the ice bed. “The suite is inspired by global warming and the overfishing that affects our oceans.” says artist Jonathan Paul Green. “I also think the idea of using frozen water from a river in northern Sweden to create an ocean with shells, fish, and corals is exciting.”

    The nearby “Haven” suite is a “magical gate of ice” guarded by two large animals. “We are inspired by the meeting between people and want to create an experience that invites curiosity and creativity, "says artist Jonas Johansson." It feels like a dream to get to work with ice that allows our love for light, shine, and reflection to wander freely from thought to creation.”

    Regardless of whether visitors select the carved suites or the basic ice rooms, the temperature is always set to a bone-chilling －5℃! That is why guests are advised to snuggle(蜷缩)up inside sleeping bags and wear gloves and winter hats all night. Not surprisingly, most end up spending just a single night at this unique hotel before moving on to the conventional and warmer hotels nearby.

    Thomas Cheatham had planned to study Latin during his time at Hebron High School in Texas. But when he learned that the school district was going to offer a Mandarin(普通话) class, he quickly changed his mind.

    "I thought Mandarin would be more beneficial than Latin," said Cheatham, who is now in his second year of studying the language.

    He speaks Mandarin to order food at Chinese restaurants and can read social media posts from his Chinese-speaking friends. While it's a difficult language to master, the high school junior, who plans to study computer engineering, thinks it will be important for his career. "Chinese is a good language to know, especially with China becoming a growing power," he said.

    Many experts agree that proficiency(熟练) in a language spoken by a billion people worldwide will give American students an edge in the global economy.

    "People are looking at China as our next economic competitor, and interest in Mandarin is growing fast," said Marty Abbott, director of the American Council(议会) on the Teaching of Foreign Languages. "We're seeing it in all parts of the country."

    Abbott predicts that as many as 100,000 students are now studying Mandarin in public and private schools throughout the US. She said the US government has designated (指定) Mandarin as an "important needs" language and provides professional development programs for teachers. "Our government wants to increase our language ability for national security and economic competitiveness," Abbott added.

    At the same time, the Chinese government is spreading knowledge of the Chinese language and culture through Confucius Institutes set up in many US states. For example, the Confucius Institute at the University of Texas in Dallas has been the home of a Confucius Institute for 10 years. It sponsors Confucius Classrooms at 21 local public and private schools, where tens of thousands of students are learning Mandarin.

In the past decade ocean oxygen levels have taken a dive — an alarming trend that is linked to climate change, says Andreas Oschlies, an oceanographer at the Helmholtz Center for Ocean Research in Germany, whose team tracks ocean oxygen levels worldwide. "We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are," he says. It is no surprise to scientists that warming oceans are losing oxygen, but the scale of the drop calls for urgent attention. Oxygen levels in some tropical regions have dropped by an astonishing 40 percent in the last 50 years, some recent studies reveal. Levels have dropped less significantly elsewhere, with an average loss of 2 percent globally.

A warming ocean loses oxygen for two reasons; First, the warmer a liquid becomes, the less gas it can hold. That is why carbonated drinks(碳酸饮料) go flat faster when left in the sun. Second, as polar sea ice melts, it forms a layer of water above colder, more salty sea waters. This process creates a sort of lid that can keep currents from mixing surface water down to deeper depths. And because all oxygen enters the surface, less mixing means less of it at depth.

Ocean animals large and small, however, respond to even slight changes in oxygen by seeking refuge(避难所) in higher oxygen zones or by adjusting behavior, Oschlies and others in his field have found. These adjustments can expose animals to new predators or force them into food-scarce regions. Climate change already poses serious problems for marine life, such as ocean acidification, but deoxygenation is the most pressing issue facing sea animals today, Oschlies says. After all, he says, "they all have to breathe."

Aside from food web problems, animals face various other physiological challenges as their bodies adjust to lower oxygen levels. Chinese shrimp(虾) move their tails less vigorously to preserve energy in lower oxygen environments. Some creatures, such as jellyfishes, are more tolerant of low oxygen than others are. But all animals will feel the impact of deoxygenation because they all have evolved their oxygen capacity for a reason, says Oschlies. "Any drop in oxygen is going to damage survivability and performance," he says.

On her 71st birthday in July, Sajean Geer went to spread her husband's ashes near Obstruction Point, inside Olympic National Park.

When she finished, she realised she had got 1 . Geer became worried. Though an experienced hiker, she wasn't prepared to be in the park for such a(n) 2 period of time. She only had her 3 

with her. She had a cellphone, but there is no signal. And worst of all, she hadn't told anyone where she was going because she hadn't 4 to be gone for long. 

She spent that first day trying to 5 her way out of the park but was unsuccessful. Geer remembered the knowledge she'd picked up from several outdoor survival books. One key tip 6 her:it's important to have a positive mental 7 and a fighting spirit that you're going to live through this. 

So she 8 what she needed. She started by constructing a shelter. She walked to a stream three times a day to get fresh 9 and lived on pine needles and even bugs(小虫). 

Ticking off the days, she 10 the six nights she and her dog had spent in the wilderness. All the while, she remained 11 , remembering that motto about a positive attitude. 

Meantime, a friend in Hawaii grew worried when she couldn't 

12 Geer for several days. She contacted Geer's brother, who asked the police to check on her. 13 , a park worker noticed her car and they began to look for her from the sky. Then they found her. When Geer was rescued, she had only a few bug bites, but 14 that, she was in good shape and spirit. 

Now, she views the experience as a good one, allowing her to learn about herself and 15 on what's important in life. 

The Chinese Tang Dynasty poet Du Fu is often called the sage(圣人) of poetry. Unlike Li Bai, this poet wrote in various styles, and his works were often innovative(创新的) in language and subject matter. His poems were also filled with meaning. 

His innovation was not at all welcome. The readers of his time rarely showed much appreciation of his original and innovative works. The masses in fact hated and scolded them. Like many artists, Du Fu was only recognised for his genius long after his death. 

Du Fu was born in Luoyang, Henan Province. Although he came from an influential literary family, his early attempts to gain a position in the government by way of the exam system failed repeatedly. He was 43 years old when he finally managed to hold an official position. This was the time when Emperor Xuanzong was attracted to the beautiful Yang Yuhuan and made her his concubine(妃子), which Du Fu severely criticised in his Song of the Beautiful Ladies. 

As the emperor got distracted from important government affairs, some military leaders were becoming too powerful. Du Fu took office in 755, and in the same year a rebel(叛乱) leader An Lushan led his army into the capital of Tang Dynasty. The emperor fled to the west and left the governing of the state to his son. Du Fu and his family took the road north to escape the rebels. 

The poet left his family and tried to get to the headquarters of the new emperor, but he was caught and held prisoner by the rebels in Chang'an. After order was restored again, Du Fu got back his position in the capital. However, he did not enjoy the favour of the new emperor and was given a minor provincial post. In 759 he finally left this disgraceful position and spent the rest of his life wandering around the country.