No one is sure how the ancient Egyptians built the pyramids near Cairo. But a new study suggests they used a little rock‘n'roll. Long-ago builders could have attached wooden pole s to the stones and rolled then across the sand, the scientists say.
“Technically, I think what they're proposing is possible,” physicist Daniel Bonn said.
People have long puzzled over how the Egyptians moved such huge rocks. And there's no obvious answer. On average, each of the two million big stones weighed about as much as a large pickup truck. The Egyptians somehow moved the stone blocks to the pyramid site from about one kilometer away.
The most popular view is that Egyptian workers slid the blocks along smooth paths. Many scientists suspect workers first would have put the blocks on sleds(滑板). Then they would have dragged them along paths. To make the work easier, workers may have lubricated the paths either with wet clay or with the fat from cattle. Bonn has now tested this idea by building small sleds and dragging heavy objects over sand.
Evidence from the sand supports this idea. Researchers found small amounts of fat, as well as a large amount of stone and the remains of paths.

However, physicist Joseph West thinks there might have been a simpler way , who led the new study . West said , “I was inspired while watching a television program showing how sleds might have helped with pyramid construction . I thought , ‘Why don't they just try rolling the things?'“A square could be turned into a rough sort of wheel by attaching wooden poles to its sides , he realized . That , he notes , should make a block of stone” a lot easier to roll than a square”.
So he tried it.
He and his students tied some poles to each of four sides of a 30-kilogram stone block. That action turned the block into somewhat a wheel. Then they placed the block on the ground.
They wrapped one end of a rope around the block and pulled. The researchers found they could easily roll the block along different kinds of paths. They calculated that rolling the block required about as much force as moving it along a slippery(滑的)path.
West hasn't tested his idea on larger blocks, but he thinks rolling has clear advantages over sliding. At least, workers wouldn't have needed to carry cattle fat or water to smooth the paths.

    Campers Gene and Marie Marsden took pride in being good citizens when in the wild. While driving miles to the Green River Lakes area, they taught their children what they had learned in the bear safety handbook put out by the Bridger-Teton Forest Service.

    Mr. and Mrs. Marsden did their best to keep a tidy camp. As the handbook had said to hang all food at least ten feet off the ground and four feet out from the trees, they did that and locked their food in their trailer(拖车) at night. It was already dark when they went to bed, but they perused the campsite with flashlights, making sure nothing was left out. Following the bear book's advice, they slept a hundred yards from where they cooked their food, and kept the car near their tents, separated from the trailer, which they left up at the other camp.

    The Marsdens liked having their dog Spike on guard. But on the first night, Spike would not stop barking. When Marie Marsden pulled the tent open and shone her flashlight, she saw a young bear.

    They all piled into the car and drove quickly down the path, calling out of the window to Spike and abandoning the trailer. They drove to a pay phone and called a Fish and Game Department guard, who identified the bear by the white ring of the fur the Marsdens had seen around his neck. The authorities informed the Marsdens that the bear was a young male that they'd been keeping an eye on.

    The next morning, the Marsdens heard helicopters circling over the mountain and wondered if it might have something to do with the bear.

    After spending the night in the public campground, they drove back to their site. Wandering the area in search of clues, Marie came to a stop below a tall tree. She slapped her head and shouted, “Oh no!”

    “What is it?” Gene asked.

    Marie pointed at the ground where Spike's dog food bowl lay upside down. A week after their return home, the Marsdens read the headline in their local paper. “Bear Killed in Wind Rivers.” According to the article, the Fish and Game Department had shot the young bear because, having been rewarded for invading(侵入) a human campsite, it would likely to do so again.

    The Marsdens knew they had been lucky in the encounter, yet much to their shame and sadness, they also knew that the bear had not.

Five years ago, when I taught art at a school in Seattle, I used Tinkertoys as a test at the beginning of a term to find out something about my students. I put a small set of Tinkertoys in front of each student, and said:"Make something out of the Tinkertoys. You have 45 minutes today and 45minutes each day for the rest of the week." A few students hesitated to start. They waited to see the rest of the class would do. Several others checked the instructions and made something according to one of the model plans provided. Another group built something out of their own imaginations.

    Once I had a boy who worked experimentally with Tinkertoys in his free time. His constructions filled a shelf in the art classroom and a good part of his bedroom at home. I was delighted at the presence of such a student. Here was an exceptionally creative mind at work. His presence meant that I had an unexpected teaching assistant in class whose creativity would infect(感染) other students.

Encouraging this kind of thinking has a downside. I ran the risk of losing those students who had a different style of thinking. Without fail one would declare, "But I'm just not creative."

"Do you dream at night when you're asleep?"

"Oh, sure."

"So tell me one of your most interesting dreams." The student would tell something wildly imaginative. Flying in the sky or in a time machine or growing three heads. "That's pretty creative. Who does that for you?"

"Nobody. I do it."

"Really-at night, when you're asleep?"

"Sure."

"Try doing it in the daytime, in class, okay?"

    When the population of the port town began to suffer from poisoning, the police came to find the cause of the poison. They thought someone was poisoning the people on purpose but no one knew how it was possible. Soon people took the position that the pork was poisoned. It was a popular food everyone ate and it could have possibly made everyone sick. Anyone who had possession of pork would throw it out. Even the poorest of the poor wouldn't eat pork. Signs were posted on poles and letters were sent to everyone to warn people of the pork. Shortly afterwards, even policemen in high positions were also getting sick.

    Soon it became political and popular. Politicians rushed to the town to talk about politics and promised how they would find the solution if they were elected. Everyone was so sick that they didn't care about politics. Everyone was in a position where he or she didn't know what to do anymore. They went to the post office to mail posts out asking for help. The poor town didn't know how to deal with the situation.

    One day, a well-known scientist from New York came to the town with a huge box containing many instruments and his possessions. He went to pools and the port and made measurements. He was quiet and polite. Then one day he made a speech at a newspaper meeting-room to announce his findings.

    “I'm sorry to say your water supply is so heavily polluted; it is poisoned. I know who has been poisoning you all for such a long time. It is you who have been poisoning yourselves with pollution. A great deal of rubbish has been thrown into the water day after day. No one here has taken good care of the environment. It is no wonder all of you have been sick.” Shocked at the news, the people present were lost in thought.

    Drug companies have spent billions of dollars searching for therapies to reverse or significantly slow Alzheimer's disease, but in vain. Some researchers argue that the best way to make progress is to create better animal models for research, and several teams are now developing mice that more closely imitate how the disease destroys people's brains.

    The US National Institutes of Health (NIH), the UK Dementia Research Institute and Jackson Laboratory (JAX) - one of the world's biggest suppliers of lab mice - are among the groups trying to genetically design more suitable mice. Scientists are also exploring the complex web of mutations(突变) that influences neurological (神经学的) decline in mice and people.

    "We appreciate that the models we had were insufficient. I think it's sort of at a critical moment right now." says Bruce Lamb, a neuro-scientist at Indiana University ~ho directs the NIH-funded programme.

    Alzheimer's is marked by cognitive impairment(认知损伤) and the build-up of amyloid-protein plaques (淀粉样蛋白块) in the brains of people, but the disease does not occur naturally in mice. Scientists get around this by studying mice that have been genetically modified to produce high levels of human amyloid protein. These mice develop plaques in their brains, but they still do not display the memory problems seen in people.

    Many experimental drugs that have successfully removed plaques from mouse brains have not lessened the symptoms of Alzheimer's disease in people. One focused stumble came last month, when three companies reported that their Alzheimer's drugs had failed in large, late-stage clinical trials. Although the drugs successfully blocked the accumulation of amyloid protein in mice, they seemed to worsen cognitive decline and brain shrinkage in people.

    The drive for better mouse models comes as genomics studies are linking the most common form of Alzheimer's to dozens of different genes. This diversity suggests that each case of the disease is caused by a different combination of genetic and environmental factors. "There is no single Alzheimer's disease," says Gareth Howell, a neuro-scientist at Jackson Laboratory (JAX) in Bar Harbor, Maine.

    Howell argues that scientists' reliance on lab mice with only a few genetically engineered mutations might have limited research. His own work suggests that in mice, just as in people, genetic diversity plays a part in determining how Alzheimer's develops.

    Some people might dream of splendid surroundings—but also need a reasonably affordable cost of living. Try one of these four astonishing spots for a magical retirement, from an International living.com report, where retirees can live well on less.

    Sintra, Portugal

    A favorite summer retreat of former royalty, which is just a 40-minute train ride from Lisbon, is the pastel-painted Palace of Pena, a 19th-century Romanticist marvel with pink turrets and daffodil-yellow tower on a hill surrounded by pine forests. A couple could live well in this arts-rich tourist town, though pricier than other cities in Portugal, on a budget of $ 3,065 a month.

    Cusco, Peru

    Cusco, Peru's most historic city, is a UNESCO World Heritage site. Once an Incan capital. Cusco has clear, sunny days. Colonial structures have been changed into fashionable restaurants, shops and even homes. Superfoods, like chia seeds, quinoa and maca, are inexpensive and plentiful. A retired couple could enjoy a good life on$ 1,700 a month.

    The West Coast, Ireland

    The Wild Atlantic Way is a cycling or driving route that stretches across the west coast of Ireland. At the heart of the route is one of the most amazing natural wonders, the landmark Cliffs of Moher in County Clare—one of Ireland's most visited natural attractions. On a budget of around $ 2, 800 a month, a retired couple could live quite comfortably.

    San Miguel de Allende, Mexico

    San Miguel was declared a UNESCO World Heritage City in 2008.The colonial centro has much to offer retirees: low cost of living, arts, charming local cultural traditions and mild weather year-round. San Miguel is a few hours' drive from Mexico City. The days are comfortably warm and the nights blessedly cool. A retired couple could live comfortably on a monthly budget of $ l, 650.