Polar bears are one of the most popular animals for people. Polar bears are different from every other bear in the world. This is because polar bears have white fur. However, there are many facts about polar bears that people might not be aware of .

    The skin of polar bears is black, which according to thinkquest.org allows them to absorb more heat from the sun. Polar bear fur is transparent , because it is made up of hollow guard hairs. Loc.gov explains that the reason polar bears display white fur is that when the sun hits the fur ,the hollow spaces in the hair scatter the light. Since none of the light is absorbed, the light reflected back appears white to human eyes.

    Polar bears' conservation status is considered close to extinction. Global warming is considered the main cause of the decline in polar population. Polar bears use ice floats to hunt for their food. However, these ice floats are melting so polar bears are starting to drown in the search for food, and the food is becoming more difficult to get. Contrary to popular belief, polar bears do not eat penguins, because polar bears are not found in the Antarctic region of the world. Polar bears are only found around the Arctic Circle. Polar bears do not drink water. They get all the water they need from the prey they eat.

    FES. Gov specifies that polar bears are considered the largest land carnivores(食肉动物) in the world. The polar bear weight ranges between 700--1,500 pounds. Since the polar bear habitat is melting away, their main evolutionary advantages are fading. Polar bears are not able to use their camouflage(伪装) to find prey in habitats not covered with snow. Polar bears do not hibernate(冬眠). However, when the weather gets uncomfortable, or mothers give birth, polar bears will dig themselves a hidden home.

    What can we do to help save the polar bears? We can donate to organizations like the World Wildlife Fund, reduce our carbon footprint, and send letters to politicians explaining to them that we need to set up more preserves to help save the polar bear habitat.

    China officially informed the World Trade Organization on Tuesday that it will ban the import of 24 different types of solid waste by the end of this year as part of a campaign to deal with environmental pollution and protect people's health.

    In response to growing public concerns over the potential environmental and health danger caused by the increasing amounts of solid waste imported into the country for recycling and treatment, China passed a special law in 1995 to control imports of waste materials, such as plastics, slag from steelmaking, unsorted scrap paper and discarded textile materials.

    A year later, the country published a list for solid waste imports and began implementing a permit system to control the import volumes and types of waste imported.

    However, due to the lack of effective supervision（监管）and the failure of relevant departments to fulfill their duties, solid waste imports have not been effectively controlled.

    So far, China is the world's largest importer of solid waste. According to the Ministry of Environmental Protection, China imported 7.3 million metric tons of plastic waste worth $3.7 billion in 2016, accounting for 56 percent of global imports of solid waste.

    Correct recycling of solid waste materials is an important part of the global economy, and moderate imports of scrap plastic, scrap paper and scrap rubber products, such as vehicle tires, can to some extent, make up for China's shortage of various raw materials.

    However, the lack of supervision has resulted in the country's severe soil and environmental worsening.

    Given that China's continuing efforts to push for industrial transformation and upgrading have resulted in a noticeable decline in the demand for the materials recycled from solid waste imports. It is right for the country to restrict such imports for the sake of the environment and public health, and to better adapt to the changed industrial structure.

    Researchers found that walking around with a forced smile and fake happiness simply leads to people feeling unhappier. So, putting a brave face on your sadness could be harmful. The research also found that women suffered more than men when pretending to be happy.

    Dr. Brent Scott, who led the study, said employers should take note because forcing workers to smile when dealing with the public can result in bad outcomes. He said, “Smiling for the sake of smiling can lead to emotional tiredness, and that's bad for the organization.” He also said the research showed customer-service workers who had “fake smiles” throughout the day didn't want to work, so their productivity dropped.

    The study is one of the first of its kind to examine emotional expressions over a period of time and compare the different effects on men and women. Dr. Scott's team examined the effects of “surface acting”, or fake smiling, compared to “deep acting”, or making people smile by thinking of pleasant memories.

    Dr. Scott said, “Women were harmed more by surface acting, meaning their moods worsened even more than men's. However, they were helped more by deep acting, which means their moods improved more by thinking of pleasant memories.”

    According to Dr. Scott women tend to suffer more when pretending to be happy because they are expected to be more emotionally expressive than men. Therefore, forcing a smile while feeling down is more likely to go against their normal behavior and cause more harmful feelings.

    Although deep acting can improve moods a little in the short term, Dr. Scott says it's not a long-term solution to feeling unhappy. There have been some suggestions that if you do this over a long period you start to feel unreal. You're trying to develop positive emotions, but at the end of the day you may not feel like yourself any more.

    Why can some people sleep through noises like a honking car or flushing toilet, while others are awakened by the lightest sound?

    To find the answer, sleep researchers at Massachusetts General Hospital conducted an unusual study of 12 self-described deep sleepers. After tests confirmed that the healthy volunteers were solid sleepers, they took part in a three-night study in the university's sleep laboratory. The participants spent the night in a big and comfortable room. But the room also included four speakers positioned near the top of the bed.

    During the night, the deep sleepers were subjected to 14 different recorded sounds, like street traffic, toilets flushing, and an airplane flying overhead. Next door, the researchers monitored their sleep patterns and brain waves.

    As expected, all of the participants slept relatively well, but there were differences in how they responded to the noisy interruptions. Some of the sleepers didn't wake up even when a sound was blasted at 70 decibels（分贝）; others were awakened by sounds at 40 or 50 decibels.

    The researchers discovered that the difference in a sleeper's reaction to noise could be predicted by the level of brain activity called "sleep spindles（纺锤体）". A sleep spindle is a burst of high-frequency brain activity coming from deep inside the brain during sleep. The source of the spindles is the thalamus（丘脑）, a part of the brain that sends sensory information to the rest of the cortex（皮层）.

    Before the study, the Massachusetts researchers theorized that the spindles are the brain's way of preventing sensory information from passing through the thalamus and waking the rest of the brain during sleep. They found that sleepers who experienced the most sleep spindles during the night were also the soundest sleepers and were least likely to be awakened by noise.

    Scientists already know that most people become lighter sleepers with age, most likely because older people experience less "slow wave sleep", which is the deepest stage of sleep. People also produce fewer sleep spindles as they age. But even when controlling for the stage of sleep a person was in, the number of sleep spindles still predicted their risk for awakening because of noise.

    More research is needed, but the findings suggest that a better understanding of sleep spindles could lead to new behavioral or drug therapies for people with sleep disorders. For example, future studies may try to determine whether diet, exercise or other behaviors may influence the number of sleep spindles a person produces during the night.

    Christmas is a great time with family and friends. One of the best ways to bond with (团结)one another is through games. So why not play some great Christmas party games?

    Present pickup is a great game for both young and young at heart. It can be played inside or outside. To prepare for the game, you will need to have some small boxes and some small gift bags. This is a great way to use the paper from last year. There should be as many presents as players. You'll also need four or more candy canes(甘蔗). Two large boxes can be used to drop the presents in.

    Two ropes will be needed. Take one rope and make a starting line. The other rope will mark the finish line. Place the large boxes at the finish line. Equally divide the presents into two groups. It's best to have an equal number of boxes and bags on each side to make it fair.

    The first player on each team will take two candy canes. When it's time to start, they'll pick up the presents only using the candy canes. Each player must run his present to the box or finish line and drop it in. If it's dropped on the way, the player starts over. After they drop their presents, the players will run the candy canes to the next players. This continues until all the presents have been picked up. The first team to finish wins.

    To play kids against adults, you may want to put easier presents in a group for the kids and more difficult ones for the adults. There are many variations to the game, so have some fun and come up with your own.

    American writer and former president of Marvel Comics, Stan Lee, has died at the age of 95. The legendary comic book author died at Cedars Sinai Medical Center in Los Angeles, according to a family lawyer.

    Lee was born in 1922 to working-class Jewish immigrants from Romania. He began working at the comics section of Timely Publications—a company that would eventually transform into Marvel Comics – and became comic editor there at age 18. At age 40, Lee decided to give up on comics. But his wife Joan urged him to create the characters he always wanted to write as his comic swansong. And in 1961, Lee and artist Jack Kirby created 'The Fantastic Four'—fascinating characters with individual personalities and the golden age of comic books began. Many Marvel characters were groundbreaking at the time. For example, Black Panther was the first black superhero featured in a mainstream US comic. Other characters he created include the Ant Man, the X-Men, Iron Man, Captain America and Doctor Strange. In its heyday (鼎盛时期), Marvel sold 50 million copies a year. Lee was also known for appearing as a cameo (配角) in every Marvel film. Fans are very happy to look for Stan Lee in the films and after watching, they will definitely have a discussion online.

    Celebrities and fans have been sharing across social media how Lee and his work affected them. The CEO of Lee's Pow! Entertainment, Shane Duffy, called him "a true iconic pioneer with no comparable second". Hugh Jackman, who played Wolverine in the X-Men films, called Lee a "pioneering force in the superhero universe". Evangeline Lilly, who portrayed Ant Man's superhero partner, the Wasp, also shared his respect on Twitter. Chris Evans, the star of Captain America, wrote on Twitter: "For decades he provided both young and old with adventure, escape, comfort, confidence, inspiration, strength, friendship and joy. He expressed love and kindness and will leave an unforgettable mark on so, so, so many lives."