Here is an astonishing and significant fact：Mental work alone can't make us tire. It sounds absurd．But a few years ago, scientists tried to find out how long the human brain could labor without reaching a stage of fatigue(疲劳). To the amazement of these scientists, they discovered that blood passing through the brain, when it is active, shows no fatigue at all!

    If we took a drop of blood from a day laborer, we would find it full of fatigue toxins (霉素) and fatigue products. But if we took blood from the brain of an Albert Einstein, it would show no fatigue toxins at the end of the day.

    So far as the brain is concerned, it can work as well and swiftly at the end of eight or even twelve hours of effort as at the beginning. The brain is totally tireless. So what makes us tired?

    Some scientists declare that most of our fatigue comes from our mental and emotional (情绪的)attitudes. One of England's most outstanding scientists, J. A. Hadfield, says, “The greater part of the fatigue from which we suffer is of mental origin. In fact, fatigue of purely physical origin is rare. ”Dr. Brill, a famous American scientist, goes even further, He declares, “One hundred percent of the fatigue of sitting worker in good health is due to emotional problems.”

    What kinds of emotions make sitting workers tired? Joy? Satisfaction? No! A feeling of being bored, anger, anxiety, tenseness, worry, a feeling of not being appreciated— those are the emotions that tire sitting workers. Hard work by itself seldom causes fatigue. We get tired because our emotions produce nervousness in the body.

    In 1947 a group of famous people from the art world headed by an Austrian conductor decided to hold an international festival of music, dance and theatre in Edinburgh. The idea was to reunite Europe after the Second World War.

    At the same time, the Fringe appeared as a challenge to the official festival. Eight theatre groups turned up uninvited in 1947, in the belief that everyone should have the right to perform, and they did so in a public house disused for years.

    Soon, groups of students firstly from Edinburgh University, and later from the universities of Oxford and Cambridge, Durham and Birmingham were making the journey to the Scottish capital each summer to perform theatre by little-known writers of plays in small church halls to the people of Edinburgh.

    Today the Fringe, once less recognized, has far out grown the festival with around 1,500 performances of theatre, music and dance on every one of the 21 days it lasts. And yet as early as 1959, with only 19theatre groups performing, some said it was getting too big.

    A paid administrator was first employed only in 1971, and today there are eight administrators working all year round and the number rises to 150 during August itself. In2004 there were 200 places housing 1,695 shows by over 600 different groups from 50 different countries. More than 1.25 million tickets were sold.

    Many of us love July because it's the month when nature's berries and stone fruits are in abundance. These colourful and sweet jewels form British Columbia's fields are little powerhouses of nutritional protection.

    Of the common berries, strawberries are highest in vitamin C, although, because of their seeds, raspberries contain a little more protein (蛋白质), iron and zinc (not that fruits have much protein). Blueberries are particularly high in antioxidants (抗氧化物质). The yellow and orange stone fruits such as peaches are high in the carotenoids we turn into vitamin A and which are antioxidants. As for cherries (樱桃), they are so delicious who cares? However, they are rich in vitamin C.

    When combined with berries of slices of other fruits, frozen bananas make an excellent base for thick, cooling fruit shakes and low fat "ice cream". For this purpose, select ripe bananas for freezing as they are much sweeter. Remove the skin and place them in plastic bags or containers and freeze. If you like, a squeeze of fresh lemon juice on the bananas will prevent them turning brown. Frozen bananas will last several weeks, depending on their ripeness and the temperature of the freezer.

    If you have a juicer, you can simply feed in frozen bananas and some berries or sliced fruit. Out comes a "soft-serve" creamy dessert, to be eaten right away. This makes a fun activity for a children's party; they love feeding the fruit and frozen bananas into the top of the machine and watching the ice cream come out below.

    You've heard the predictions from some of the brightest minds about AI's influence. Tesla and SpaceX chief Elon Musk worries that AI is far more dangerous than nuclear weapons. The late scientist Stephen Hawking warned AI could serve as the "worst event in the history of our civilization" unless humanity is prepared for its possible risks.

    But many experts, even those who are aware of such risks, have a more positive attitude, especially in health-care and possibly in education. That is one of the results from a new AI study released Monday by the Pew Research Center.

    Pew canvassed the opinions of 979 experts over the summer, a group that included famous technologists, developers, innovators and business and policy leaders. The interviewed experts, some of whom chose to remain anonymous, were asked to join in the discussion of a serious and important question: "By 2030, do you think it is most likely that advancing AI and related technology systems will improve human capacities and control them?"

    Nearly two-thirds experts predicted most of us will be mostly better off. But a third thought otherwise, and a majority of the experts expressed at least some concerns over the long-term impact of AI on the "essential elements(要素) of being human." Among those concerns were data abuse, loss of jobs and loss of control brought by autonomous weapons and cybercrime(网络犯罪). Above all, by taking data in and spitting answers out, those "black box" tools make decisions in digital systems. It is an erosion(侵蚀) in our ability to think for ourselves.

    Over the past century, an alarming number of animals have become endangered or even extinct. Below are some animals whose numbers have been rapidly dropping in recent years.

    Panda Bear

    One of the biggest reasons contributing to the decline in the panda species is the destruction of its natural habitat. Farmers in China have gradually been claiming more and more of the land. As a result, pandas are forced to move away to places where it is hard to find bamboo for food.

    Green Turtle

    The green sea turtle species has survived for several millions of years, so you might wonder why it's only becoming endangered now. A major cause is the change in climate and temperature, which both affect the hatching rates of turtle eggs. Climate changes also cause violent weather and rising water levels to flood areas where turtles usually go to lay their eggs. Apart from this, oil spills and other poisonous pollution, as well as increased fishing activities can cause sickness, or even death to the green turtles.

    Cheetah

    Cheetahs are famous for being the fastest animal on land but even they can't run from some of the larger threats that have harmed them. Like the panda bears, cheetahs have gradually been losing their natural homes due to humans claiming land and developing in those areas. To make matters even worse, smaller animals move away when these areas are occupied, which means that the cheetah has less food! Don't forget that other large animals, such as lions, are also fighting for any food that they can find, so occasionally young cheetahs end up as prey too.

    Indian Elephant

    Elephants are extremely intelligent animals and also the largest mammals that live on land. Sadly, in Asia many elephants were killed so that people could remove their tusks to use as decorative objects. While this practice has been banned now, some people still illegally continue. Forests in India have also been steadily destroyed and elephants are sometimes killed when they end up on human territory.

    Have you ever imagined what it would be like to see the world through an animal's eyes? For example, what a chimpanzee sees as it sits at the top of a tree, or a penguin's view as it dives into the sea to catch its dinner?

    These questions are answered in the nature documentary Animals with Cameras, produced by the BBC. The three-part series was first aired in the UK last month. To explore animal stories "told" by the animals themselves, the documentary's filmmakers worked with scientists to develop cameras that wild animals could wear.

    "Never before have we seen such high-quality footage (连续镜头)directly from the animal's point of view, " BBC Nature executive producer Fred Kaufman told PBS." This miniseries greatly expands our comprehension of animal behavior and this camera technology opens up new possibilities for discovering so much more."

    Indeed, the groundbreaking technology provides a new viewpoint of the animal kingdom. New cameras with enough battery life to shoot for hours at a time were designed to be comfortable enough for animals to wear, according to the documentary's camera designer Chris Watts.

    The technical challenges didn't stop there. Some animals were very curious about the equipment, with some even fighting each other for the chance to wear a camera. In the case of chimpanzees, "we had to create dummy (仿造的)cameras, so that every chimpanzee could get one", the miniseries' wildlife cameraman Gordon Buchanan told Live Science.

    For animals that were comfortable enough to be with human beings, the cameras could be fitted and removed by hand. But for others, the cameras came off automatically using a timed release and were collected afterward. This meant that the cameras needed to be as tough as possible.

    To avoid disturbing the animals, scientists who were good at dealing with wildlife came to help by putting the cameras on the animals." The last thing we want to do is cause them distress." the documentary's producer Dan Rees told the BBC. "To follow an animal in the first place, there had to be a clear benefit in terms of knowledge about it that might be useful to protecting a species in the future.

    Their efforts certainly paid off. " Footage that captures (捕捉)these rare and exciting glimpses of animals bidden habits is important to scientists, but documentaries like Animals with Cameras also resonate with (引起共鸣)audiences, connecting them with the beauty - and danger - of wildlife in their natural environments," Live Science noted.