In some countries，open campus (校园) is widely accepted. For example, French students have a two-hour lunch break from 11:30 a.m. to 1:30 p.m. During their lunch break, they can eat at home or at a restaurant. But students in the Philippines have a tougher schedule. They have only two 15-minute breaks and an hour for lunch.

    What Schedule would be best for American schools?

    Having breaks between classes is great, but having breaks off campus is even better. There are several advantages to open campus, including simple conveniences such as being able to eat different meals during lunchtime, rather than having the cafeteria (自助食堂) dishes, as well as having the chance to take a break at home.

    However, there are more reasons I disagree with allowing high school students the right to have an open campus. Sure, it's great being able to escape school during the day for a while, but soon enough that may easily become the rest of the day.

    If open campus is allowed, it is very possible that such freedom will make it all too easy for students to skip their afternoon classes. Of course, there will be students responsible enough to come back to school.

    But unexpected problems such as heavy traffic, city bus delays (延迟) or cars breaking down may prevent them from returning to school. It benefits the students to stay in school during lunch hours to avoid transportation issues.

    Depending on how close the school is to restaurants and students' homes, open campus could be a great idea. Unfortunately, though, most public schools in America are not located close enough to restaurants or students' homes, thus causing the negative results to outweigh (超过) the positives in the end.

    “Image is everything.” An entire industry has been built upon the concept that image is everything, but an appealing image isn't enough when there's no substance behind it.

    First of all, one should consider how important image is in selling products and services. Advertising agencies have raised the art of creating an image to a state of near perfection. But if the product or service doesn't live up to it, customers will be very dissatisfied. The recent scandal (丑闻) about the Arthur Andersen accounting firm showed that behind that image, it had unfair business practices under the table. Despite the previous positive image, the firm is being accused of criminal actions. Although the image had been nearly perfect, the reality behind the image has led to its downfall.

    Similarly, personal consultants(顾问) can build up a very positive public image for politicians and movie stars in the view of the general commons. But once again, history is filled with examples of both that fell from grace (体面) like the story of the Hollywood actor giving in to the pressures of fame and fortune. With people, just as with products and services, image is certainly important, but without positive substance behind it, failure is close.

    To conclude, it's clear that an appealing image is extremely important to success, whether that image is related to selling a product or service or to the “selling” of a person. But image is only half of the equation(等式). What lies behind that image is every bit as important as the image itself — the person or product must live up to that image or there's little chance for long-term success.

    If all the food that's thrown away in three American cities could be saved, it would provide 68 million meals for people who don't have enough to eat, according to a recent study.

    The researchers found that, in the cities they surveyed（调查）, more than a kilogram of edible food per person is wasted each week. Edible food is food you can eat. It doesn't include things like apple cores（果核）, egg shells, or bones from meat. Fruits and vegetables were the most common edible foods found in the dustbin, followed by food leftover from meals. Eggs, bread and milk were also commonly thrown out.

    The people taking part in the survey gave several reasons for throwing edible food away. Most said the food went off. Some said they weren't interested in eating leftovers. A few said the food had passed the “Best Before” date printed on the label（标签）. When food is wasted—by families, restaurants or grocery stores—we are also wasting all of the resources that go into producing that food. That means we are wasting water, land, energy and labour, as well as the fuel needed to transport food.

    A lot of food is wasted before it even reaches the grocery store（食品杂货商）. Some food is damaged while it is being transported from the farm to the stores. Fruits and vegetables that don't look attractive enough don't even get put onto the shelves because most people won't buy them. Grocery stores, restaurants and hospitals also waste a large amount of food. The researchers suggest that grocery stores should donate any food that is still okay to eat to homeless shelters, instead of throwing it away. Prepared meals from hospitals or restaurants could also be donated to shelters.

    “I could see a huge flow (流动) of water, coming down fast from very high. I had no idea of shape, or situation, or anything. It was just so big.”

    These are the words of the great English writer Charles Dickens. He wrote them when he was visiting Niagara Falls. This waterfall is on the border (边界) of the United States and Canada. It is one of the largest in the world, and the largest in North America.

    Niagara Falls is on the Niagara River. The river divides just before the waterfall, and there are actually three waterfalls. On the American side are American Falls and Bridal Veil Falls. Horseshoe Falls is mostly on the Canadian side. The name comes from its shape — like a horseshoe, in a half circle. Horseshoe Falls is the widest of the three.

    People mainly know about Niagara Falls because of its size and natural beauty. However, the Niagara River is also an important source of electricity.

    In the 1890s, the Westinghouse Electric Company built a large power system (电力系统) on the river. Many other companies also hoped to use the land around Niagara Falls for factories and power systems. However, around the same time, many people began to work to protect the natural area. Soon, the governments of the United States and Canada got involved with it. They protected the land around Niagara Falls. They made parks — green, natural areas. No one could buy this land for factories. For hundreds of years, millions of people have visited Niagara Falls to enjoy its beauty.

    More than 40 percent of the species that help with pollination (植物传粉) are under threat due to the polluted environment. So some researchers have been searching for ways to protect the bees and other crucial pollinators while some engineers have thought perhaps an army of robotic pollinators could keep humans well-supplied in these foods. A team of researchers has recently designed a small drone capable of pollinating flowers. They tested their device on the large, pink flowers of lilies. And it worked.

    Exciting as this success was, it is only the first step. The team has yet to figure out how to apply the concept on the massive scale. Could a fleet of robo-pollinators replace the bees?

    “Although the answer isn't a straightforward no, it would be a challenging leap to go from this one little drone pollinating one large flower to an army of drones spreading across fields of crops,” says Scott Swinton, an agricultural economist at Michigan State University.

    “The successful pollination was fascinating,” Scott Swinton says, “but the device itself might damage the flowers. I wonder how you make sure you're not doing more harm than good to flowers when you have a drone.”

    “Furthermore,” he points out, “a lily is a particularly easy flower for a drone to pollinate. To make this more broadly applicable for smaller and more complex flower structures, the drones would need to be particularly agile.”

    Still, Joshua Campbell, an expert at the University of Florida, says “Pollination systems are extremely complex and will always require insects. There is no substitute for bees.”

    “As for the technology itself, it is a promising new development in existing drone technology,” he added. Yet he still sees some hurdles ahead before drones can be applied on a large scale.

    A tiny clue found in ancient deposits has unlocked big secrets about Greenland's past and future climate. Just beyond the northwest edge of the vast Greenland Ice Sheet, researchers have discovered lake mud that have survived the last ice age. The mud, and remains of common flies in it, record two interglacial periods(间冰期)in northwest Greenland.

    Although researchers have long known these two periods—the early Holocene and Last Interglacial—experienced warming in the Arctic, the mix of fly species shows that Greenland was even warmer than previously thought. "As far as we know, it has never been found in Greenland. We think this is the first time anyone has reported it in ancient deposits or modern lakes there," Axford said. "We were really surprised to see how far north it migrated (迁徙)."

    This new information could help researchers better measure Greenland's sensitivity to warming, by testing and improving models of climate and ice sheet behaviour. Those models could then improve predictions of how Greenland's ice sheet might respond to man-made global warming. After all, Greenland covers 80 per cent of the Arctic country and holds enough ice to equal 20 feet of global sea level. "Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in every coastal city around the world," said Yarrow Axford, an associate professor in the team. "One of the big uncertainties in climate science is how fast the Earth changes when it gets warmer. Geology gives us an opportunity to see what happened when the Earth was warmer than today," said Axford.

    People might be surprised to see how today's Greenland looked during the last two interglacial periods. During the Last Interglacial, global sea levels increased by 15 to 30 feet, largely due to thinning of Greenland and Antarctica's ice sheets. However, now researchers believe northern Greenland's ice sheet experienced stronger warming than previously thought, which could mean that Greenland is more responsible for that sea-level rise.

    Finding lake deposits older than about 10,000 years, however, has been historically very difficult in Greenland. To measure these ancient temperatures, researchers look to ice cores (冰核) and lake deposits. Since ice and lake deposits form by a gradual buildup on annual layers of snow or mud, these cores contain history of the past. By looking through the layers, researchers can obtain climate clues from centuries ago.