Plastic is easy, convenient, cheap and long-lasting, but it does great harm to the environment.

    Since plastic entered mass production, 8 billion tons have been produced – and we aren't very good at recycling. By 2015, 6,945 tons of plastic waste had formed, with around 9 percent of it getting recycled. About 79 percent of it ends up in landfills or around the environment, including the ocean. We may end up drowning in plastic before long.

    Chemists at Colorado State University have found a polymer（聚酯）that has many of the qualities of plastics – it's light, strong, durable and heat-resistant – but that can be changed back to its original small-molecule（分子）state for complete recycling. Even after being recycled, the polymer can be turned back into its plastic-like state, and this can be done quickly and cheaply.

    This new polymer has all the good qualities of plastics, yet it is relatively easy to make and to recycle. Making it requires room temperature conditions, a short reaction time to bond the monomer（单体）into polymers and only a small amount of the catalyst（催化剂）remains in the end product. It has a high molecular weight, stands up to heat and generally behaves like plastic. Recycling it requires similarly little effort. Mild lab conditions are required and so is a catalyst. Once applied, the polymers are once again monomers in a matter of minutes and can be used to create another product.

    But don't get too excited about this just yet. Scientists stressed that the polymer isn't ready for mass products just yet. There's still plenty of development to do, including making it more economical to produce and recycle.

    Since the first Earth Day in 1970, Americans have gotten a lot “greener” toward the environment. “We didn't know at that time there even was an environment, let alone that there was a problem with it,” says Bruce Anderson, president of Earth Day USA.

    But what began as nothing important in public affairs has grown into a social movement .Business people, political leaders, university professors, and especially millions of grass-roots Americans are taking part in the movement. “The understanding has increased many, many times,” says Gaylord Nelson, the former governor from Wisconsin, who thought up the first. According to US government reports, emissions (排放)from cars and trucks have dropped from 10.3 million tons a year to 5.5 tons .The number of cities producing CO beyond the standard has been reduced from 40 to 9. Although serious problems still remain and need to be dealt with, the world is a safer and healthier place. A kind of “Green thinking” has become part of practices.

    Great improvement has been achieved. In 1988 there were only 600 recycling programs; today in 1995 there are about 6,600. Advanced lights, motors, and building designs have helped save a lot of energy and therefore prevented pollution.

    Twenty –five years ago, there were hardly any education programs for environment. Today, it's hard to find a public school, university, or law school that does not have such a kind of program. “Until we do that, nothing else will change!” say Bruce Anderson.

    Crossing your legs is an extremely common habit; most people don't even notice that they're doing it when they sit down. While you may find it comfortable to sit with one knee crossed over the other, it might be causing health problems that you are not aware of.

    A study published in Blood Pressure Monitoring stated that sitting with your legs crossed can increase your blood pressure. The reason for this is that the blood in your legs has to work against gravity to be pumped back to your heart and that crossing one leg over the other increases resistance(阻力), making it even harder for the blood to circulate. This causes your body to increase your blood pressure to push the blood back to the heart. You won't feel any immediate effects, but repeated, drawn­out increases in blood pressure can cause long­term health problems. So, planning to sit for a long period of time? Don't keep your legs crossed.

    Crossing your legs at the knee can also cause pressure on the major nerve in your leg that passes just below your knee and along the outside of your leg, explains Richard Graves, a medical expert. This pressure can cause numbness and temporary paralysis (麻痹) of some of the muscles in your foot and leg, preventing you from being able to raise your ankle—what we know as that "pins and needles" sensation. While the feeling of discomfort may only last a minute or two, repeatedly crossing your legs until they feel numb can cause permanent nerve damage.

    So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.

    The idea that computers have some amount of "intelligence" is not new, says Ralph Haupter, the president of Microsoft Asia, pointing as far back as 1950 when computer pioneer Alan Turing asked whether machines can think. "So it has taken nearly 70 years for the right combination of factors to come together to move AI from concept to reality," says Haupter.

    It is predicted that the development of artificial intelligence will be the story of the coming generations, not just the coming year, but as 2019 gets underway, you'll find AI will begin to touch your life in many ways according to some researchers.

"Personal assistant AIs will keep getting smarter. As our personal assistants learn more about our daily routines, I can imagine the day I need not to worry about preparing dinner. My AI knows what I like to eat, which days of the week I like to cook at home, and makes sure that when I get back from work all my groceries are waiting at my doorstep, ready for me to prepare that delicious meal I had been longing for." —Alecjandro Troccoli, senior research scientist, NVIDIA.

"Thanks to AI, the face will be the new credit card, the new driver's license and the new barcode (条形码). Facial recognition is already completely transforming security with biometric capabilities being adopted, and seeing how technology and business are connected, like Amazon is with Whole Foods, I can see a near future where people will no longer need to stand in line at the store." —Georges Nahon, president, Orange Institute, a global research laboratory.

"2019 will be the year AI becomes real for medicine. By the end of the year we're seeing solutions for population health, hospital operations and a broad set of clinical specialties quickly follow behind." —Mark Michalski, executive director, Massachusetts General Hospital.

    Nature calms our stressed-out soul. Nature is the best medicine, but new research is showing how little time we need to set aside to harvest the benefits.

    In one new study, researchers tried to find the most effective "dose" (药剂) of nature within the context of normal daily life. As more doctors prescribe (开药方) nature experiences for stress relief and other health benefits — sometimes referred to as a "nature pill"— the study's authors hoped to make the details of these treatments clear.

    "We know that spending time in nature reduces stress, but until now it is unclear how much is enough, how often to do it, or even what kind of nature experience will benefit us," says lead author MaryCarol Hunter in a statement. "Our study shows that for the greatest payoff, in terms of efficiently lowering levels of the stress hormone cortisone (压力荷尔蒙激素), you should spend 20 to 30 minutes sitting or walking in a place that provides you with a sense of nature."

    A nature pill can be a low-cost, low-risk way to curb the negative effects of urbanization and indoor lifestyle. To find the most efficient dosage, Hunter and her co-authors asked 36 city citizens to have nature experiences of at least 10 minutes three times per week over eight weeks.

    Every two weeks, the researchers collected saliva (唾液) samples to measure levels of the stress hormone cortisone, both before and after the participants took a nature pill. The data showed that just a 20-minute nature experience was enough to significantly reduce cortisone levels. The effect was more efficient between 20 and 30 minutes, after which benefits continued to increase but at a slower rate.

    That fits with the findings of another recent study, which found that spending 20 minutes in an urban park can make you happier, no matter whether you use that time to exercise.

    For this study, 94 adults visited 3 urban parks in Mountain Brook, Alabama, completing a questionnaire about their subjective well-being before and after their visit. An accelerometer (加速计) tracked their physical activity.

    A visit lasting 20 to 25 minutes showed the best results, with a roughly 64% increase in the participants' self-reported well-being, even if they didn't move a great deal in the park. That last point is particularly positive, since it means anyone can benefit from visiting a nearby park, whatever his or her age or physical ability.

    "There is increasing pressure on green space within urban settings," said a UAB professor Gavin Jenkins. "Planners and developers look to replace green space with residential (住宅的) and commercial property. The challenge facing cities is that there is increasing evidence about the value of city parks but we continue to see the disappearance of these spaces."

    A dog spent the last four years of his life waiting a crossroad in the Thai city of Khon Kaen as if waiting for someone. People originally thought the dog had been abandoned, but then realized that he looked healthy, so people asked around about him. It turned out that the dog had indeed been spending most of his time around that crossroad, but a woman had been coming round regularly to bring him food and water.

    One day, while photographing the dog everyone called Leo, a reporter met the woman who had been taking care of him. She had come to drop off some food. After learning the story about the dog and the woman, the reporter decided to share the story on social media. The post soon went viral and the photos of Leo got shared hundreds of times. And the photos reached the eyes of Leo's former old owner.

    Nang Noi Sittisarn, a 64-year-old woman from Thailand's Roi Et Province, almost had a heart attack when her daughter showed her a photo of the beloved dog named BonBon she had lost during a car trip. When she learned that he had been waiting for her in the same spot for the last four years, her heart melted(融化).

    Auntie Noi told her daughter to drive her to where the dog was waiting. When she got there and called his name. BonBon, the poor dog started wiggling(扭动)his tail and came to her, but when she tried to take him home with her, he was unwilling to follow. She didn't want to force the dog to come with her so she agreed to leave him with his new master. However, she and her daughter will come to visit him regularly.