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You drink diet soda enjoying the sweet taste without the guilt of calories. But scientists have long suspected a link between artificial sweeteners(甜味剂)and obesity in humans. A new study suggests that artificial sweeteners may not be as harmless as once thought. They may not only disturb the microbes(微生物)living in the bodies of humans, but some may even increase the risk of weight gain. 

Every human hosts a unique group of microbes. The number of cells that make up this vast community, called microbiome(微生物群), is extremely large in the human body. It not only helps digestion but also protects against diseases. The disturbance to the microbiome occurs because artificial sweeteners, although zero calories for humans, serve as nutrients for some microbes, which then increase rapidly. This causes an imbalance in microbial populations that can lead to diseases. 

In the study, scientists first chose 1,375 volunteers to see if they consumed artificial sweeteners in their daily lives. Then, they identified 120 volunteers who were not previously exposed to artificial sweeteners and gave them one of the four commonly used sweeteners—saccharin, sucralose, aspartame, and stevia for two weeks. After that, to test how artificial sweeteners affect the body's ability to control the sudden increase of blood sugar after consuming sugar as part of meals, volunteers were monitored for blood glucose(血糖)levels after a test glucose drink.

The study showed that sucralose and saccharin pushed the body towards glucose intolerance, which, if sustained, can cause weight gain. However, aspartame and stevia did not affect glucose tolerance at the tested levels. "The study is the first to show that the human microbiome responds to artificial sweeteners. It's also a convincing study to show how these sweeteners really are affecting the human body," says Michael Goran, a professor at Children's Hospital Los Angeles.

"This study provides evidence of both short-term harmful effects and long-term negative effects caused by artificial sweeteners," David Katz, a nutrition specialist, says. "That does not mean artificial sweeteners should be replaced with sugar. Rather, alternative approaches to reducing sugar intake should be considered. "

Taylor grew up on the coast of New South Wales, Australia and swimming in the ocean was part of everyday life. She began spear fishing and worked her way up in her early 20s to become one of very few women who were professional spear fishers and was named the Australian Ladies National Champion. 

However, as she spent more time underwater, especially with the sharks, she had a change of heart. "I learned straight away that sharks are nowhere near as dangerous as the media would have us believe. And I learned that they all have different personalities-there's the shy guy, the cross guy, and the aggressive guy; they're all different. " From that point on, she decided, along with her late husband and world spear fishing champion, Ron Taylor, to hang up her spear and to only shoot them with her camera.

As a pioneering shark conservationist, Taylor succeeded in many firsts throughout her life's work. She was the first person to dive with sharks cageless. The first person to test the power of a shark bite; she hand-fed a Great White and petted it. There's nothing she wouldn't do to help correct the false image that sharks are dangerous, man-eating beasts. Her research has become the basis for much of what we know about sharks today and she succeeded in becoming the first person to get Grey Nurse sharks protected in a specific area, the first shark species in the world to receive protected status.

When asked about what could be done to help save the sharks, and the oceans, Taylor said she was quite pessimistic about the whole thing. "Change has to come from the government level. "But she also recommended, "The thing that works the best is to get a good story and then get it on camera. Then go on television and speak to the public. Say it to the mothers, "Wouldn't you like your child…when they're old enough, to be able to see this wonderful, friendly shark?"

Invasive Species Management

Placencia, Belize

Make a difference by removing lion-fish, an invasive species destroying reef ecosystems of the Caribbean. Learn to dive while removing lion-fish. Each week/day will differ but you will be participating in the following areas; Removing Invasive Lion-fish. Whale Shark Observation(if spotted). Biodiversity Identification Dive. Beach Clean-ups. 

Marine Research Expedition

Tyrrhenian Sea, Italy

You will join an international crew aboard a sailboat to work for the protection of our seas. And you will learn to collect data, organize and enjoy the sea at its best! Experience the sailing life in one of the world's best spots for Water sports. Gain experience in Marine Research in the field(Under water). Get close up to dolphins and whales in the wild.

Wildlife Supporter

Port Elizabeth, South Africa

Volunteer at a Game Reserve that hosts the Big 5 and support the local staff in monitoring the animals. Work up close with the famous Big 5! Join our reserve for orphaned and injured non dangerous animals. Make a difference in the rescue, rehabilitation (康复) and release of wildlife giving them a second chance at being free and wild again. 

Climate and Environmentalist Supporter

Hanga Roa, Chile

Be a volunteer on the amazing Easter Island in the middle of the Pacific Ocean and get involved in climate and nature protection. Responsibilities include: Teamwork in the climate protection program, Collection of plant seeds, Control of seed settlement on the plantation, Conservation of native seeds and plants, Reforestation work. 

注意： 
1.写作词数应为80左右； 
2.为使行文连贯，可以适当增加细节。

Illegal ivory (象牙) hunting once posed a significant threat to Kenya's elephants. But now the giants of the animal kingdom (face) an even bigger risk: climate change.

In the past years, Kenyan (official) have cracked down on hunting,  has targeted giraffes for their meat, bones and hair and elephants for their ivory tusks. But as Kenya battles its worst drought in four decades, the crisis is killing 20 times more elephants  hunting. In Tsavo Nationai Park much wildlife (flee) in recent years in search of water. To survive, elephants require vast landscapes for food. Adults can consume 300 pounds of food and more than 50 gallons of water  day. But rivers, soil and grassland are drying up,

(result) in poor and deadly environment.

In the last year, at least 179 elephants have died of thirst, while hunting has claimed the lives of fewer than 10, Kenyan Tourism and Wildlife Secretary Najib Balala told the BBC. "It is a red alarm." he said of the crisis. Balala suggested that much time and effort has been spent tackling illegal hunting that (environment) issues have been ignored. "We have forgotten to invest into biodiversity (manage) and ecosystems," he said. "Something must be done to deal with climate change."

Human beings have somehow managed to engineer the night to receive us by filling it with light. This kind of control is no different from the feat(壮举)of damming a river. Its benefits come with 1  — called light pollution — whose effects scientists are only now beginning to study. Light pollution is largely the result of bad lighting design. 2  lighting washes out the darkness of night, altering light levels and light rhythms to which many forms of life, including ourselves, have 3 . Wherever man-made light spills into the natural world, some aspects of life-migration, reproduction, feeding-is affected.

For most human history, the phrase "light pollution" would have 4 . Imagine walking towards London on a moonlit night around 1800, when it was Barth's most populous city. Nearly a million people lived there, 5 candles, torches and lanterns, as they always had. Only a few houses were lit by gas, and there would be no public gaslights in the streets or squares for another seven years. From a few miles away, you would have been more likely to 6 London than to see its dim collective glow.

We've lit up the night as if it were a(n) 7 country. As a matter of fact, among mammals (哺乳动物) alone, the number of species active at night is astonishing. Light is a powerful biological force, and on many species it acts as a magnet attracting them to it. The effect is so powerful that scientists speak of songbirds and seabirds being 8 by searchlights on land or by the light from gas flares on marine oil platforms, circling and circling in the thousands until they drop.

It was once thought that light pollution only affected astronomers, who need to see the night sky in all its glorious clarity. Unlike astronomers, most of us may not need a 9 view of the night sky for our work. 10 , like most other creatures, we do need darkness. 11 darkness is pointless. It is as essential to maintaining our bioiogical welfare as 12 itself; the price of modifying our internal clockwork means it doesn't operate as it should, causing various physical discomforts. So fundamental are the regular rhythms of waking and sleep to our being that 13 them is similar to altering our center of gravity.

In a very real sense, light pollution causes us to 14  our true place in the universe, to forget the scale of our being, which is best 15  against the dimensions of a deep night with the Milky Way—the edge of our galaxy—arching overhead.

There are few natural sounds more uplifting to my spirit than the bright and cheering calls and songs of black-capped chickadees (山雀). One of my morning routines is to step outside the house and listen for the voices of black-caps.

There is something comforting to me in black-caps' presence. Sometimes they are the only birds I'll hear on my local wood land walks and for me the forest would be a lonelier place without them.

After I'd moved into a house on Anchorage's Hillside, I placed a makeshift feeder on my home's back. For each, the routine was similar: dashed in, looked around, pecked（啄） at the tray, looked around again, and dashed out. Nervous little creatures, full of bright energy, they soon had me laughing at their funny way. By the time they moved on, I sensed an all-too-rare up welling of fascination and joy.

Within days, a whole new world opened up as woodland neighbors I'd never known, or even imagined, joined the black-caps at my feeders: red-breasted nuthatches, common red-polls ... What was remarkable was that all of those species were common residents of the Anchorage area.

My newfound interest in birds grew quickly, surprising even me. I visited bookstores in search of birding guidebooks. Excitedly exchanged bird descriptions with a stranger. Purchased 50-pound bags of sunflower seeds. All of this seemed very strange to a middle-aged guy who'd never been attracted by birds. Even more, I had previously judged bird watchers to be rather dull sorts.

They've reminded me how my world can expand and become enriched when I make the effort to pay attention. What else awaits me in our world, I wonder, that I haven't yet discovered or noticed?

A. Nature always amazed me in its own way.

B. Yet in prior days and years, I had no idea.

C. Black-caps have had a special place at the top of my affections.

D. Within a day, black-caps accepted my invitation to dine.

B. Black-caps are a sign of good environment.

F. What started as mere curiosity flowered into a consuming passion.

G. And much more often than not, they are heard before they' re seen.

Google's parent company is winding down a project that used high-lying balloons to provide Internet services to hard-to-reach areas of the world.

The project, known as Loon, started in 2011. It was managed by Alphabet Inc. It aimed to bring connectivity to areas of the world where ground-based cell towers (手机信号塔) were too expensive or too difficult to set up.

But Loon was unable to reduce costs enough to make its business model run, the project' s leader, Alastair Westgarth, said in a blog post. "While we've found a number of willing partners along the way, we haven't found a way to get the costs low enough to build a long-term, competitive business," Westgarh said.

Loon's shutdown isn't surprising, economists said.

Loon's technology sent gas-filled balloons the size of tennis courts into the air. They usually stay at heights of around 60, 000 to 75,000 feet. There, onboard communications equipment sent Internet signals back down to earth. The system was able to offer mobile coverage to an area 200 times larger than a traditional ground-based cell tower. However, a carrier would need several balloons at once, each would cost tens of thousands of dollars and last only about five months.

Alphabet wasn't alone in running projects aimed at offering Internet connection to hard-to-reach areas. Companies such as Amazon. com Inc. and Elon Musk's SpaceX have been making efforts to provide Internet connection in such places, using satellites in near Earth orbit.

Over the last few years, Loon's technology has proved successful in some suffering communities. In 2017, the project sent balloons into the skies above Puerto Rico after a terrible hurricane damaged the island's communications facilities. Two years later, soon after a 7. 8 earthquake struck parts of Peru, Loon's balloons began to provide the locals with mobile connectivity.

Rich Devaul, a founder of the project, said the need for mobile connectivity was rapidly rising recently. This made cell towers more cost-effective than he had expected ten years ago, reducing the need for Loon, "The problem got solved faster than we thought," he said in an interview.

Do the colors that surround you influence how you feel? Can the colors on your walls and on your clothes affect your moods? Some researchers believe the answer is a decisive yes, while others aren't so sure.

Yet many marketers, interior designers, medical professionals and others swear by an informal field of science known as color psychology. Color psychology is defined as "the study of how the colors we perceive impact our thoughts and feelings."

Marketers use the science of color to persuade us to buy things. When choosing paint, furniture and wall art, interior designers act on the theory that colors can arouse certain feelings in us. Dentists are often advised to use light blue paint on their office walls to help calm apprehensive patients.

We should keep in mind, though, that only by considering cultural preferences are we able to fully understand the science of color. For instance, in the West, white is for brides and black is for funerals. But in ancient Asia, white was sometimes worn for funerals. In Japan yellow represents courage while in the United States, it represents happiness. Additionally, many variables including gender, age, background and more must be considered before making color assumptions when one is studying the effects of color.

After taking color variable into account it's safe to consider some mainstream theories about specific colors and their meanings. Here are just a few:

Red symbolizes love, energy, passion and danger. Red is also believed to increase one's hunger, which might be the reason why McDonald's and Coca-Cola chose red as their major branding color.

Brown, a color from nature, best represents things that are honest, trustworthy and dependable. It seems a perfect fit as the branding color for the package delivery company UPS.

Blue-in addition to representing peace and calm-also means integrity and competence. It's no surprise that PayPal and American Express both use blue as their branding color.

Green-another color from nature-represents health, growth and freshness and is the perfect branding color for Starbucks.

Pink symbolizes love, romance, innocence and femininity (女性特质). The popular doll company that makes Barbie uses pink as its major branding color.

If color psychology advocates are correct, then our emotions and decisions are truly influenced by the colors around us. With this knowledge, we can effectively harness (驾驭) color power to create positive school, work and home environments.

"Sunshine might be healthier than most people think, outweighing the risk of skin cancer", British doctors suggested last week. The four researchers at Bristol University were accused of weakening years of campaigning to warn people of the dangers of too much sun. Experts agree exposure to the sun's ultraviolet rays increases the risk of skin cancer and accelerates the signs of aging. But in the British Medical Journal the Bristol team led by Andrew Ness wrote, "There is evidence that the potential benefits of exposure to sunlight may outweigh the widely publicized negative effects on the incidence of skin cancer."

Vitamin D, made in the body in reaction to sunlight, prevented rickets (软骨病) in children and was associated with a protective effect against heart disease.

Sunshine was also useful for treating certain skin conditions and there was also the "feel good effect of lying or sitting in the sun". The researchers said it was too early to advise people to spend more time in the sun, but suggested the basis of the current advice to cover up should be reviewed.

"Perhaps, while we await the conciusions of such formal analyses, those of us who enjoy spending time in the sun can rest assured that the chance that we will be one of the people dying from the sun small." they added.

Their article was strongly criticized by health campaigners who claimed it was unbalanced and not backed by scientific evidence. Britain's Health Education Authority said skin cancer was the most common form of cancer in the country, with more than 50, 000 new cases diagnosed each year and more than 2, 000 people dying from the disease. It said treatment almost always required surgery and almost 50 percent of cases were fatal. The authority's skin cancer campaign manager Christopher New said, "We are very disappointed with this controversial article." It doesn't have enough supporting evidence and runs the risk undoing many years of "good health education".