When you go to the doctor, you like to come away with a prescription．It makes you feel better to know you will get some medicine. But the doctor knows that medicine is not always needed. Sometimes all a sick person needs is some reassurance that all will be well. In such cases the doctor may prescribe a placebo.

    A placebo is a sugar pill, a harmless shot, or ail empty capsule. Even though they have no medicine in them, these things seem to make people well. The patient thinks it is medicine and begins to get better. How does this happen?

    The study of the placebo opens up new knowledge about the way the human body can heal itself. It is as if there was a doctor in each of us. The doctor will heal the body for us if we let it. But it is not yet known just how the placebo works to heal the body. Some people say it works because the human mind fools itself. These people say that if the mind is fooled into thinking it got medicine, then it will act as if it did, and the body will feel better.

    Placebos do not always work. The success of this treatment seems to rest a lot with the relationship between the patient and the doctor. If the patient has a lot of trust in the doctor and if the doctor really wants to help the patient, then the placebo is more likely to work. So in a way, the doctor is the most powerful placebo of all.

    A placebo can also have bad effects. If patients expect a bad reaction to medicine, then they will also show a bad reaction to the placebo. This would seem to show that a lot of how you react to medicine is in your mind rather than in your body. Some doctors still think that if the placebo can have bad effects it should never be used. They think there is still not enough known about it.

    The strange power of the placebo does seem to suggest that the human mind is stronger than we think it is. There are people who say you can heal your body by using your mind. And the interesting thing is that even people who swear this is not possible have been healed by a placebo．

    You may know about “junk food” like French fries. But do you know about “junk sleep”?

    Recently, a British survey found that electronic(电子的) products in teenagers bedrooms are affecting(影响)their sleep.

    The survey was done among 1,000 British kids from 12 to 16. It found that 30 percent of them got just 4 to 7 hours sleep every day. But doctors say they need 8 to 9 hours.

    Almost a quarter of the kids said they fell asleep more than once a week while watching TV, listening to music or using other electronic products.

    “This is very worrying.” said Dr Chris Idzikowski, a British expert, “We call it 'junk sleep', it means you don't get enough sleep and the quality of the sleep is bad, too. If you don't get good rest, you don't perform well in school the next day.”

    The survey found that 40 percent of the kids felt tired each day, with girls between 13 and 16 feeling the worst. Nearly all the teenagers have a phone, Mp4 or TV in their bedroom. And many of them have all three.

    Even plant can run a fever, especially when they're under attack by insects or disease. But unlike human, plants can have their temperature taken from 3,000 feet away straight up. A decade ago, adopting the infrared（红外线） scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely（精确的） target pesticide（杀虫剂） spraying rather than rain poison on a whole field, which always includes plants that don't have pest problems.

    Even better, Paley's Remote Scanning Services Company could detect crop problems before they became visible to the eye. Fixed on a plane flown at 3,000 feet at night, an infrared scanner measured the heat sent out by crops. The data were transformed into a color﹣coded map showing where plants were running "fevers". Farmers could then spot﹣spray, using 50 to 70 percent less pesticide that they otherwise would.

    The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted the new technology and long﹣term supporters were hard to find. But with the renewed concern about pesticides on produce and refinements（改进） in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt that the technology works. "This technique can be used on 75 percent of agricultural land in the United States," says George Oerther of Texas A&M, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial support which he failed to obtain 10years ago.

    Escaping predators (食肉动物), digestion and other animal activities—including those of humans—require oxygen. But that essential ingredient is no longer so easy for marine life to obtain, several new studies reveal.

    In the past decade ocean oxygen levels have taken a dive—an alarming trend that is linked to climate change, says Andreas Oschlies, an oceanographer at the Helmholtz Center for Ocean Research in Germany, whose team tracks ocean oxygen levels worldwide. "We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are," he says. It is no surprise to scientists that warming oceans are losing oxygen, but the scale of the drop calls for urgent attention. Oxygen levels in some tropical (热带的) regions have dropped by an astonishing 40 percent in the last 50 years, some recent studies reveal. Levels have dropped less significantly elsewhere, with an average loss of 2 percent globally.

    A warming ocean loses oxygen for two reasons: First, the warmer a liquid becomes, the less gas it can hold. That is why carbonated drinks go flat faster when left in the sun. Second, as polar sea ice melts, it forms a layer of water above colder, more salty sea waters. This process creates a sort of lid that can keep currents from mixing surface water down to deeper depths. And because all oxygen enters the surface, less mixing means less of it at depth.

    Ocean animals large and small, however, respond to even slight changes in oxygen by seeking refuge in higher oxygen zones or by adjusting behavior, Oschlies and others in his field have found. These adjustments can expose animals to new predators or force them into food-scarce regions. Climate change already poses serious problems for marine life, such as ocean acidification, but deoxygenation is the most pressing issue facing sea animals today, Oschlies says. After all, he says, "they all have to breathe."

    Aside from food web problems, animals face various other physiological challenges as their bodies adjust to lower oxygen levels. Chinese shrimp (虾) move their tails less vigorously to preserve energy in lower oxygen environments. Some creatures, such as jellyfishes, are more tolerant of low oxygen than others are. But all animals will feel the impact of deoxygenation because they all have evolved their oxygen capacity for a reason, says Oschlies. "Any drop in oxygen is going to damage survivability and performance," he says.

Los Angeles Could Be One Of The Few Cities The Olympics Can't Ruin

    In just the past several years, six cities—Boston; Rome; Stockholm; Hamburg, Germany; Krakow, Poland; and Oslo, Norway—have decisively rejected the idea of hosting the Olympics.

    The games' high costs, damaging effects on poor communities in the places that have recently hosted them have turned cities, against them—fostering the belief that "nobody wants to host the Olympic Games anymore."

    But Los Angeles is different. And on Wednesday, the Los Angeles City Council made final decision to try to get the chance to host the 2024 Olympics, taking the step Boston and many others never did. In LA, organizers promise they can hold an Olympics that stays within its $5.3 billion budget Organizers in every possible host city make the same promise. But when it comes to LA, where residents greatly support the plan, even people who doubt the Olympics believe that success in hosting the Olympics without any loss might be possible. "It's basically sound," said Smith College economist Andrew Zimbalist, who wrote the book on the financial risks the Olympics bring to cities and their taxpayers. "I think they'll be able to do it without any financial downside, although there is always some risk attached."

    There's another reason to believe LA could succeed: It's done it before. It last hosted the Olympics in 1984, when the Olympic turned a small profit. No host since has replicated that feat.

    The Los Angeles Coliseum, which was used for the 1932 and 1984 Olympics, will again serve as the place of the games, along with a new NFL stadium set to open in Inglewood in 2019. There's no need for a new Olympic village, thanks to dorms at UCLA. When LA announced its final three stadiums this month, chairman Casey Wasserman said proudly that a Los Angeles Olympics won't require any new construction—instead, it will rely entirely on already planned or temporary (临时的) places.

    You may have heard that humans only use ten percent of their brain, and that if you could unlock the rest of your brainpower, you could do so much more. You could become a super genius, or acquire psychic powers like mind reading.

    This "ten-percent myth" has inspired many references in the cultural imagination. In the 2014 movie Lucy, for example, a woman develops godlike powers thanks to drugs that release the previously inaccessible 90 percent of her brain.

    Contrary to the ten-percent myth, however, scientists have shown that humans use their entire brain throughout each day.

    Over the years, brain scientists have shown that different parts of the brain are responsible for specific functions, whether it's recognizing colors or problem solving. Contrary to the ten-percent myth, scientists have proven that every part of the brain is integral for our daily functioning.

    Research has yet to find a brain area that is completely inactive. Even studies that measure activity at the level of single neurons(神经元) have not revealed any inactive areas of the brain.

    Many brain imaging studies that measure brain activity when a person is doing a specific task show how different parts of the brain work together. For example, while you are reading this text on your smartphone, some parts of your brain, including those responsible for vision and reading comprehension, will be more active.

    A more direct counter to the ten-percent myth lies in individuals who have suffered brain damage – like through a stroke(中风)– and what they can no longer do, or do as well, as a result of that damage. If the ten percent myth is true, then damage too many parts of our brain shouldn't affect your daily functioning. Studies have shown that damaging a very small part of the brain may have devastating consequences.

    If someone experiences damage to Broca's area(布罗卡氏区), for example, they can understand language but can't speak fluently.

    In one highly publicized case, a woman in Florida permanently lost her" capacity for thoughts, perceptions, memories, and emotions that are the very essence of being human" when a lack of oxygen destroyed half of her brain.