Distance runners often worry about “hitting the wall” during training or races—that terrible moment when negative thoughts become so overpowering that they make it difficult to continue.

Hitting the wall typically happens around 20 miles in a marathon, when the body's supplies become exhausted. At this point, many runners feel exhausted and discouraged, slow their pace, have trouble focusing and want to quit or walk.

“Generalized tiredness, unintentionally slowing their pace, the desire to walk, and shifting focus to just surviving the marathon appear to be particularly common characteristics of it,” said Dr. Alistair McCormick, an exercise psychologist in England who co-authored a new study. “A marathon becomes a real mental battle when runners ‘hit the wall.'”

    Psychological blocks are an extremely common experience for recreational endurance (耐力) athletes, according to the study. To learn how they affect people, sports psychologists asked 30 recreational runners and cyclers about the psychological demands of training, preparing for and participating in competitions.

     “Recreational runners and cyclists found it stressful trying to find the time to train, McCormick said. “What was also interesting was the number of potential banana skins they met with before and during competition-disasters that could cause the athletes to lose their focus and their motivation to keep persevering.”

    These roadblocks included difficult environmental conditions and equipment failure, problems with nutrition or making a mistake, the study reported. The athletes in the study said they fell these obstacles (障碍) affected their motivation and concentration, negatively affecting their overall performance.

According to the study, 43 percent of marathoners are likely to hit the wall during a race. Finding ways to move past those kinds of experiences, then, could have major benefits for an athlete's performance and well-being.

    The discussion on renewable energy has been going on for at least a decade and people have relied on fossil fuels almost entirely for more than a century. However, the situation when fossil fuels were the most efficient and the cheapest source of energy has been left far in the past. Many countries such as Germany and Sweden have already made significant efforts to fix this situation, employing numerous power plants working on the renewable resources of energy. The most effective among these resources is geothermal（地热的）energy.

    Geothermal energy does not depend on the world's economic and political situation as strongly as fossil fuels do. Besides, extracting（提炼）fossil fuels adds to the price of energy produced from them. Therefore, geothermal energy is much cheaper than traditional ones, saving up to 80% of the costs over fossil fuels.

    Being a renewable resource, geothermal energy produces less waste and pollution than traditional energy sources. In geothermal systems, carbon dioxide makes up about 10% of air produced. Overall, in order to produce the electricity that can be used for one hour, the geothermal systems produce 0.1 pound of carbon dioxide and other harmful gases. For a comparison, a power plant producing from gas produces up to 2 pounds of carbon dioxide into the atmosphere, and those power plants that work on coal（煤）produce an astonishing 3.6 pounds of greenhouse gases.

    Low costs is another reason why using geothermal power plants should be the first choice for many countries. Geothermal heat systems require 25% to 50% less energy for work compared with the traditional systems for heating or cooling. Besides, geothermal equipment is less big: due to the very nature of geothermal energy, geothermal power plants have only a few moving parts, all of which can be easily sheltered inside a relatively small building. What's more, the life span of geothermal equipment is rather long. All these make geothermal power stations easy to build and keep.

    Larger brain size linked to longer life in deer. The size of a female animals' brain may determine whether they live longer and have more healthy later generations, according to new research led by the University of Cambridge.

    The study, published in the Royal Society Open Science journal, shows that female red deer with larger brains live longer and have more surviving later generations than those with smaller brains. Brain size is heritable and is passed down through the generations. This is the first extensive study of individual differences in brain size in wild mammals and draws on data comparing seven generations of deer.

    Across species of mammals, brain size varies widely. This is thought to be a consequence of specific differences in the benefits and costs of a larger brain. Mammals with larger brains may, for example, have greater abilities that enable them to adapt better to environmental changes or they may have longer lifespans. But there may also be disadvantages: for instance, larger brains require more energy, so individuals that possess them may show reduced ability to give birth to young babies.

    The researchers, based at the University of Cambridge's Zoology Department and Edinburgh University's Institute of Evolutionary Biology, wanted to test if they could find more direct genetic or non-genetic evidence of the costs and benefits of large brain size by comparing the longevity(长寿) and survival of individuals of the same species with different sized brains. Using the skulls of 1,314 wild red deer whose life histories and breeding success had been monitored in the course of a long-term study on the Isle of Rum, they found that females with larger endocranial volumes(脑腔容量) lived longer and produced more surviving offspring in the course of their lives.

    Lead author Dr Corina Logan, a Gates Cambridge Scholar, says, "The reasons for the association between brain size and longevity are not known, but other studies have suggested that larger brains are a consequence of the longer-lived species having longer developmental periods in which the brain can grow. These predictions were generated from cross-species correlations; however, testing such hypotheses requires investigations at the within-species level, which is what we did. "

    Dr Logan adds, "We found that some of the cross-species predictions about brain size held for female red deer, and that none of the predictions were supported in male red deer. This indicates that each sex likely experiences its own set of trade-offs(权衡,协调) with regard to brain size. "The study also showed that females' relative endocranial volume is smaller than that of males, despite evidence of selection for larger brains in females.

    Professor Tim Clutton Brock, who set up the Rum Red Deer study with Fiona Guinness in 1972 and started the work on brain size, points out, "The reason that this kind of study has not been conducted before is that it requires long term records of a large number of individuals across multiple generations and data of this kind are still rare in wild animals."

    A recent experiment proves that bees can save time and energy when they fly around to different flowers.

    Dr Nigel Raine, from the Royal Holloway University of London, has always been interested in finding out why animal behave like they do. He is also interested in bees. It was not a surprise when he and some other scientists from Queen Mary University of London discovered that bees can quickly solve a problem that takes computers many days.

    Flowers make pollen (花粉), and when bees visit them, they carry the pollen to other flowers. The plants need the pollen to make seeds that will grow. Dr Raine notes that we get a lot of our food from plants, so it is important to know how the bees move around and take the pollen between flowers. The scientists wanted to examine the journey that the bees take and how they save energy when they do this. They completed the experiment on the roof of Queen Mary University, using artificial flowers and a large amount of nectar, a sweet liquid produced by flowers. They taught one bee to visit all the flowers in one place at the same time. When the bee got to know the location of the flowers well, they saw how it flew around and returned home with the nectar. After this, they changed the locations of the flowers. The scientists thought the bee would follow the route it knew already. This would mean that it followed a longer route than it needed to, and so it would use more energy. They watched the bee carefully as it travelled between the flowers in their new location, and they made notes. But in the experiment, the bee changed its route and flew a shorter distance.

    The problem that the bee solved is similar to a maths puzzle called the 'travelling salesman problem'. A salesman who goes to different places to sell things wants to travel the shortest distance. But he has to calculate the length of many possible routes to know which one is the shortest. A computer can calculate this but the experiment shows bees can do the same calculation quickly with a tiny brain. Scientists are very interested in how they do this. It would help us to understand how pollen is moved around. In addition, if they find this out, it could help us to improve communication networks. This might help humans to reduce traffic jams when there is an accident, for example.

    The world is a greener place than it was 20 years ago. A study published in the journal “Nature Sustainability” said that recent satellite data reveals a greening pattern that is strikingly prominent in China and India. The study shows that human activity in China and India dominates this greening of the planet, thanks to tree planting and agriculture. The effect comes mostly from ambitious tree-planting programs in China and intensive agriculture in both countries.

    “China and India account for one-third of the greening,” said lead author Chi Chen of Boston University. “ That is a surprising finding, considering the vague idea of land degradation (毁坏) in populous countries from overexploitation,” added Chen.

    China alone accounts for 25 percent of the global net increase in leaf area with only 6.6 percent of global vegetated area. The greening in China is from forests (42 percent) and croplands (32 percent), but in India, it is mostly from croplands (82 percent) with minor contribution from forests (4.4 percent).

    China's outsized contribution to the global greening trend comes in large part from its programs to conserve and expand forests with the goal of preventing land degradation, air pollution, and climate change.

    “Once people realize there is a problem, they tend to fix it,” said Rama Nemani, research scientist and co-author of the study. “In the 1970s and 80s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. Now we see that humans are contributing.”

    Land area used to grow crops is comparable in China and India—more than 770, 000 square miles—and has not changed much since the early 2000s. Yet these regions have greatly increased both their annual total green leaf area and their food production.

    This was achieved through multiple cropping practices, where a field is replanted to produce another harvest several times a year. Production of grains, vegetables, fruits and more have increased by about 35%～40% since 2000 to feed their large populations.

Any visitor to the Chinese Culture Week being held at the University of Tehran would be amazed by the Chinese tea, food, and various artworks produced through Chinese knotting and {#blank#}1{#/blank#}(tradition) paper cutting — all displayed by Iranian students learning Chinese.

The Chinese Culture Week aims {#blank#}2{#/blank#}(introduce) Chinese culture to more Iranians. Held inside the lobby of the institute, which {#blank#}3{#/blank#}(establish) in 2009, the event displayed a range of artworks that contain different {#blank#}4{#/blank#}(element) of Chinese culture, produced by Iranian professors and students at the university.

"{#blank#}5{#/blank#}(give) China's increasing global influence, as well as its friendly and expanded relations with Iran, learning about the country directly is becoming {#blank#}6{#/blank#}(vital) important," said Hamed Vafaei, the Iranian director of the Confucius Institute at the University of Tehran. He believes that the students who are studying {#blank#}7{#/blank#} Chinese language at the institute will enter different sectors of Iranian society in the near future, helping more people to get to know more about China.

China is the world's second-largest economy, the most populous country, {#blank#}8{#/blank#} a permanent member of the UN Security Council, so learning Chinese has become a necessity as many around the world have realized, he said.

"Each of the students here is a window toward China, {#blank#}9{#/blank#}(help) the Iranian people have a more realistic picture of the country, which will make {#blank#}10{#/blank#} possible to improve bilateral relations in the long run," he added.