Scientists are debating how to limit their newly-discovered power to change genetic structure (结构). Scientists already modify the genes (基因) of farm animals and agricultural plants to make them more productive or stronger. But now they can also change genes in wild animals and plants. These genes would continue into later generations. For example, it may be possible for scientists to remove from existence the kind of mosquitoes, small flying insects, that carry the Zika virus. They might also be able to permanently remove species (物种) of plants and animals that are damaging to other species.

    In a report published last week, the U. S. National Academies of Sciences, Engineering and Medicine (NAS) said it supports continued research on this kind of gene control. But it warned that it is not possible to know what will happen when these changed plants and animals are released (释放) into the wild.

    Sixteen biologists, ethicists (伦理学家) and policymakers are on an NAS committee that is examining the issue. They say that there is value to the new technology. But, they say, there is not enough evidence to support the release of modified organisms (生物体) from the laboratory into nature.

    Many people would support stopping mosquitoes and rats from carrying diseases. But scientists say we must understand the possible scientific, ethical, legal and social results of such action before we decide whether to take it. Gene modification is spread through reproduction (繁殖).

    Changed genes will continue to spread as long as an animal or plant continues to reproduce. They cannot be limited to a farm or kept within a country's borders. Scientists are wondering what may happen if a modified organism mates with another species. They are not yet sure how the modified genes would affect the other species. It is possible that those genes could harm those creatures or even lead to their disappearance from our planet.

    China is using travel as an important tool to help strengthen its economy. At the recent First World Conference on Tourism a Chinese official spoke about the government's plan for using tourists and the money they spend. The head of China's National Tourism Administration, Li Jinzao, said that China plans to send 150 million travelers along what he called the “One Belt, One Road”. In the next five years, these tourists are expected to spend $200 billion, he said. This spending estimate is likely to raise expectations among countries along the ancient Silk Road, which links China to its neighbors.

    China has reasons to feel it can use tourism to influence the foreign policy. Governments across the world are changing their immigration(移民) rules to welcome the growing numbers of Chinese tourists. Chinese citizens are now going to places where in the past Chinese rarely went. Marketing expert Michel Gutsatz said that among Chinese travelers, South Korea and Thailand are popular destinations. Outside of Asia, he said, Chinese are more likely to visit Europe than North America. These changes, he said, are the results of young Chinese travelers, who spend more and travel independently.

    Spending by Chinese tourists has lifted the economies of several Asian countries, including Thailand, Malaysia and Vietnam. It is expected that the number of Chinese traveling overseas to reach 242 million by 2024. In a single year, that number would be equal to the total number of tourists received by Germany, Iran, Indonesia and Egypt combined.

    China is now the biggest business travel market in the world. The Global Business Travel Association (GBTA) recently announced that China has overtaken the United States in business travel. Chinese spent just over $290 billion. This year, GBTA predicts that the Chinese business travel market will grow over 10 percent, while the US business travel market will grow less than 2 percent.

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    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."