The main cause of death and disability in the US

    Stroke (中风) is the main cause of death and disability in the United States. Every 45 seconds, someone in America has a stroke. {#blank#}1{#/blank#} It is the nation's third leading cause of death, ranking behind diseases of the heart and all forms of cancer. The following is something more about stroke.

Definition and description of a stroke

    Stroke is a type of cardiovascular disease. It affects the arteries(动脉) leading to and within the brain. A stroke occurs when a blood vessel（血管） that carries oxygen and nutrients to the brain is either blocked by a clot or bursts. {#blank#}2{#/blank#} So stroke forms.

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    The American Stroke Association has identified several factors (因素) that increase the risk of stroke. The more risk factors a person has, the greater the chance that he or she will have a stroke. Some of these you can't control, such as increasing age, family health history, race, and previous stroke. {#blank#}4{#/blank#} Factors resulting from lifestyle or environment can be improved with a healthcare provider's help.

Breakthroughs in treatment

    {#blank#}5{#/blank#} In fact, about 600,000 people have strokes every year. For many years, there was no hope for those suffering a stroke. However, recent breakthroughs have led to new treatments. For the treatments to work, the person must get to a hospital immediately.

    I'll admit I've never quite understood the obsession (难以破除的成见) surrounding genetically modified (GM) (改变) crops. To environmentalist opponents, GM foods are simply evil, an understudied, possibly harmful tool used by big agricultural businesses to control global seed markets and beat local farmers. They argue that GM foods have never delivered on their supposed promise, that money spent on GM crops would be better channeled to organic farming and that consumers should be protected with warning labels on any products that contain genetically modified ingredients. To supporters, GM crops are a key part of the effort to sustainably provide food to meet a growing global population. But more than that, supporters see the GM opposition of many environmentalists as fundamentally anti-science, no different than those who question the basics of man-made climate change.

    For both sides, GM foods seem to act as a symbol: you're pro-agricultural business or anti-science. But science is exactly what we need more of when it comes to GM foods, which is why I was happy to see Nature devote a special series of articles to the GM food controversy. The conclusion: while GM crops haven't yet realized their initial promise and have been dominated by agricultural businesses, there is reason to continue to use and develop them to help meet the enormous challenge of sustainably feeding a growing planet.

    That doesn't mean GM crops are perfect, or a one-size-fits-all solution to global agriculture problems. But anything that can increase farming efficiency—the amount of crops we can produce per acre of land—will be extremely useful.GM crops can and almost certainly will be part of that suite of tools, but so will traditional plant breeding, improved soil and crop management—and perhaps most important of all, better storage and transport infrastructure (基础设施) especially in the developing world.(It doesn't do much good for farmers in places like sub-Saharan Africa to produce more food if they can't get it to hungry consumers.) I'd like to see more non-industry research done on GM crops—not just because we'd worry less about prejudice, but also because seed companies like Monsanto and Pioneer shouldn't be the only entities (实体) working to harness genetic modification. I'd like to see GM research on less commercial crops, like corn. I don't think it's vital to label GM ingredients in food, but I also wouldn't be against it—and industry would be smart to go along with labeling, just as a way of removing fears about the technology.

    Most of all, though, I wish a tenth of the energy that's spent endlessly debating GM crops was focused on those more pressing challenges for global agriculture. There are much bigger battles to fight.

    Honey (蜂蜜) from the African forest is not only a kind of natural sugar, it is also delicious. Most people, and many animals, like eating it. However, the only way for them to get that honey is to find a wild bees' nest (巢) and take the honey from it. Often, these nests are high up in trees, and it is difficult to find them. In parts of Africa, though, people and animals looking for honey have a strange and unexpected helper—a little bird called a honey guide.

    The honey guide does not actually like honey, but it does like the wax (蜂蜡) in the beehives (蜂房). The little bird cannot reach this wax, which is deep inside the bees' nest. So, when it finds a suitable nest, it looks for someone to help it. The honey guide gives a loud cry that attracts the attention of both passing animals and people. Once it has their attention, it flies through the forest, waiting from time to time for the curious animal or person as it leads them to the nest. When they finally arrive at the nest, the follower reaches in to get at the delicious honey as the bird patiently waits and watches. Some of the honey, and the wax, always falls to the ground, and this is when the honey guide takes its share.

    Scientists do not know why the honey guide likes eating the wax, but it is very determined in its efforts to get it. The birds seem to be able to smell wax from a long distance away. They will quickly arrive whenever a beekeeper is taking honey from his beehives, and will even enter churches when beeswax candles are being lit.

    Beyoncé Knowles can do something that many humans struggle with: sing and dance at the same time. But, it turns out this great ability is not unique to humans. The superb lyrebird, already known to be a gifted singer, can perform coordinated(协调的)song­and­dance routines(一套舞蹈动作)that put most humans to shame.

    The superb lyrebird is one of only two lyrebird species living in Australia, the other named Albert's lyrebird. Male lyrebirds have tails in the shape of an ancient musical instrument when spread out. Like most animals with beautiful body parts, the males use their tails to attract females. Each one sets up a small mound(小丘)on the forest floor, where he walks around proudly and sings. He also shows his tail by holding it over his head.

    Lyrebirds are gifted mimics(模仿者), so their songs combine their own calls, the songs of other species, and sounds they have heard in the forest. That would be enough showing off for other animals, but male superb lyrebirds also dance.

    Anastasia Dalziell of the Australian National University in Canberra filmed 12 lyrebirds in the wild. She found that males only danced during four song types, and that each song type was accompanied by a specific move. “Lyrebirds match different dance styles to different types of songs, ”she says. For example, when the male sang a series of rapid notes he also stepped to the side and held his tail wide. Another song type was accompanied by jumping and moving up and down, with the tail held narrow.

    “Our results suggest that the coordination between song and dance—like movements we see in humans can occur in other animals,” says Dalziell. Female lyrebirds might prefer males that are better at coordinating song and dance, although there is no evidence of that yet.

    A Chinese scientist's attempt to produce the world's first gene-edited babies who are immune to HIV has caused floods concern.

    In an online video posted on Monday, He Jiankui, a biological researcher, announced that a pair of twin baby girls, Lulu and Nana, was born healthy a few weeks ago with genetic editing technology that can prevent them from being infected with HIV.

    He, who was believed to be in Hong Kong on Monday to attend the Second International Summit on Human Genome Editing, could not be reached for comment. But his announcement sparked a heated argument concarning medical ethics（伦理）and effectiveness.

    The Shenzhen Health and Family Planning Commission said on Monday evening that it had not received any ethical assessment application for the study, which is required as a prior condition for such experiments.

    More than 120 scholars from universities and institutes with high status from China and abroad,such as Tsinghua University and the Massachusetts Institute of Technology (MIT),strongly condemned the research in a signed statement, saying the “research” lacks effective ethics inspection, and it amounts to human experimentation,which is “crazy”.

    In the statement, published on Sina Weibo, the scientists said any attempt to make changes to human embryos with genetic editing and give birth to such babies involves high risk as an inevitable part, due to inaccuracies in existing genetic editing technologies.

    “Scientists all over the world dare not make such attempts due to the huge risks and more importantly, ethics. The government must make quick legal moves to strictly supervise（监督）such research. The Pandora's Box has been opened, and we may still have a chance of closing it before it is too late,”the statement said.

    Tsui Lap-chee, president of the Academy of Sciences of Hong Kong, said a lot of issues may occur in gene editing. If one gene is edited, it will affect others that interact with it. And the whole genome, a collection of genes, may also be affected.

    China and India are leaders in improving global(全球的) tree cover, a new study based on NASA research showed.

    They took a 31.8% part together of the total global new leaf area between 2000 and 2017. China played a major role, adding 25% to this increase, and India added 6.8%, followed by Canada and Russia. The study in the Nature Sustainability journal shows that more than 5.5 million square kilometers of green leaf area was added globally. Since 2000, there has been a five-percent increase in global green cover, it said.

    "The greening over the last twenty years shows an increase in leaf area on plants and trees which is as large as the area of the entire Amazon rainforest," Chi Chen, a Boston University researcher and lead of the study told Nature Sustainability. Large plantation activities to protect forests in China contributed nearly 42% to the country's green cover, and agriculture added another 32%. In India, 82% of the increase in leaf area was because of agriculture.

    "China and India take up one-third of the greening, but hold only nine percent of the planet's land area covered in green plants," Chi Chen told NASA Earth Observatory. "That is a surprising finding, considering the land degradation(退化) in countries with large populations."

    Boston University's research team first detected an increase in global green cover in the 1990s but were unsure about what contributed to the increase. Finally, with the help of NASA's Terra and Aqua satellites research, they managed to find out the increase in leaf cover from different areas and places.