“This is your last chance,” warned Mrs Gillfeather. I broke out in a sweat and my hands started to shake. We both wanted to get to sleep, but before we could, I had to put a cannula(针管) in her arm.

    Before becoming a doctor I'd only a vague idea what a cannula was, coming from an hour spent with a plastic arm while at medical school. Once I became a doctor, however, I couldn't seem to get away from them.

    For those of you who are lucky enough to have never come into contact with one, they're tiny little tubes that are put into a vein(静脉)so that fluid or medicines can do directly into the blood. That's the theory. Unfortunately, the problem is that for them to work, you have to get them into the vein in the first place. This tends to be trickier than you'd imagine—and it's a job that tends to fall on the junior doctors.

    Mrs Gillfeather's veins were particularly elusive that evening. I'd been jabbing the needle in for at least 20 minutes.

    “Isn't there someone else who could do this?” she asked, for the fourth time. “Someone who knows what they're doing, perhaps,” she said under her breath, just loud enough for me to hear.

    Finally, I got it in. Mrs. Gillfeather and I both breathed a sigh of relief

    Just as I was about to leave the ward, the nurse called me over, “Max, there's another cannula to do on bed 16.”

    It is important to protect yourself from harmful rays. But if you think a high-factor sunscreen keeps you safe from harmful rays, you may be wrong. Research in this week's Nature shows that while factor 50 reduces the number of melanomas（黑瘤）and delays their occurrence, it can't prevent them. Melanomas are the most aggressive skin cancers. You have a higher risk if you have red or blond hair, fair skin, blue or green eyes, or sunburn easily, or if a close relative has had one. Melanomas are more common if you have periodic intense exposure to the sun. Other skin cancers are increasingly likely with long-term exposure.

    There is continuing debate as to how effective sunscreen is in reducing melanomas – the evidence is weaker than it is for preventing other types of skin cancer. A 2011 Australian study of 1,621 people found that people randomly selected to apply sunscreen daily had half the rate of melanomas of people who used cream as needed. A second study, comparing 1,167 people with melanomas to 1.101 who didn't have the cancer, found that using sunscreen routinely, alongside other protection such as hats, long sleeves or staying in the shade, did give some protection. This study said other forms of sun protection – no sunscreen – seemed most beneficial. The study relied on people remembering what they had done over each decade of their lives, so it's not entirely reliable. But it seems reasonable to think sunscreen gives people a false sense of security in the sun.

    Many people also don't use sunscreen properly applying insufficient amounts, failing to reapply after a couple of hours and staying in the sun too long. It is sunburn that is most worrying – recent research shows five episodes of sunburn in the teenage years increases the risk of all skin cancers.

    The good news is that a combination of sunscreen and covering up can reduce melanoma rates, as shown by Australian figures from their slip-slop-slap campaign. So if there is a heat wave this summer, it would be best for us, too, to slip on a shirt, use sunscreen and slap on a hat.

    To see the world is one thing; to have someone to share it with is another. Indeed, travel becomes more interesting when you have a travel partner. A travel partner can be a close friend, a family member, a pal you've met online, or a business friend.

    You can have someone to talk to.

    Traveling alone is fun, but wouldn't you feel lonely？Having a travel partner can remove the feeling of loneliness. This is especially true if you can get a travel companion who is very familiar with the place you're traveling to. You don't have to ask any information from the locals, and you can increase the time you spend in the country.

    __________________________

    One of the major headaches in traveling is the costs involved. You can't simply ignore the rising price of hotels or plane tickets. You should also think about your daily needs, such as your food. Of course, you can't simply go back without bringing any souvenirs (纪念品) to your friends and family. All these can ruin your budget. However, when you have a travel friend, you can have someone to share the expenses with.

    You can meet a good friend.

    Having a travel mate is a good way of meeting a new friend or even a lifelong partner. You can never count the number of couples who actually found their way into each other's heart while traveling together in another country.

    You can have someone to watch out for you.

    When you're in a foreign land, you'll never be really safe. You don't know the rules as well as the culture of the people. A travel mate will be perfect to remind you of your duties in the country and to watch your back just in case you get lost.So why don't you find a travel companion now?

    Let's find out how...

    Every summer, my family and I visit our relatives in India and whenever we travel, my parents always remind me to drink only bottled or boiled water. On one of my trips to India, I saw children drinking water from the roadside. I was troubled to learn that millions of people, most of them children in developing countries, die each year because of water related diseases.

    Living in the US, I am lucky to be able to turn on the tap and get potable water(饮用水), while one sixth of the world's population lacks access to clean water This year, I entered the Discovery Education 3M Young Scientist Challenge. In late June, I learned that I was selected as one of the top 10 national finalists of this famous middle school science competition. Over the summer, I worked with Dr. Jim Jonza, my Scientist mentor(导师 )from 3M, and developed a system that uses solar energy to purify water. My invention is green and cost effective, and I am looking forward to implementing this in places that are affected(影响)by harmful water pollution.

    In October, my family and I flew to 3M Headquarters in St Paul, Minnesota, where the final event was to be held. For the last challenge, each of us had to present the invention we had been working on over the summer. The first place winner would win $25,000, a trip to Costa Rica, and the title of America' Top Young Scientist. At the awards ceremony, all of us waited anxiously until one of the judges, Danny Forester, started announcing "The winner of the Discovery Education 3M Young Scientist Challenge is…" You could hear a pin(大头针) drop as he opened the paper with the winner' s name, "Deepika Kurup!"

    As America's Top Young Scientist, I was given an opportunity to show my invention on national television and deliver several presentations. One of the most important things I have learned is that communication and teamwork are key to success.

    Scientists recently discovered three tyrannosaur (霸王龙) trackways in Canada. The trackways suggest the meat eaters traveled and hunted in groups. The 70-million-year- old footprints are the first tyrannosaur trackways ever found.

    Tyrannosaurs were a type of meat-eating dinosaur that included the strong Tyrannosaurus rex and Albertosaurus. “Groups of tyrannosaurs may have stuck together as a group to increase their chances of bringing down animals and individually surviving,” study coauthor Richard McCrea says. He works for Canada's Peace Region Paleontology Research Centre. It's believed that tyrannosaurs were solitary creatures. The newly discovered trackways could change the way scientists look at these frightening beasts.

    Trackways can uncover a lot about the social behavior of a species. Unfortunately, very few tyrannosaur footprints have ever been found, and until recently, the only ones known were single prints discovered in Mongolia, the western U.S., and western Canada. But in October 2011, a hunting guide named Aaron Fredlund found two tyrannosaur track marks near Tumbler Ridge, an area in the foothills of the Canadian Rockies. Over the next year, McCrea and his team searched the site and found the remaining trackways.

    The footprints are at about the same depth, which suggests the tyrannosaurs moved through the area at the same time. Impressions of the dinosaurs' rough skin are even visible in the prints. The prints are also in near-perfect condition. That's because the ground had a high clay (黏土 ) content when the dinosaurs walked through the area. The land was later covered by a thick layer of volcanic ash, which kept the marks intact (完整). "This is the most ideal situation you could ask for," McCrea says.

    Researchers aren't sure of the exact species of tyrannosaur that left the prints. But the historic findings show a great deal about how the beasts moved and behaved. “We have extremely convincing evidence that tyrannosaurs traveled in groups,” says McCrea. "This is probably the most important evidence to come out to date on that topic."

    The school year has barely started in Denver, and French teacher Tiffany Choi is already worried that her students are suffering from absent-mindedness. The problem isn't texting, playing video games or passing notes. It's Denver's ongoing heat wave.

    "Today was a little bit hot, so I noticed kids were very sleepy and they were having to get up to drink water quite often." said Choi, who works at Denver's East High School. "If you lose too much water, and you have to keep going to the water fountain, that can take away from their classroom experience." While nodding off in class on a warm day may seem like a right of passage for the average teen, Choi's observation carries a bigger consequence than parched (干燥的) lips.

    "There's been quite a few media reports about teachers noticing that students weren't able to focus on hotter days," said R Jisung Park, a researcher, "Does a hotter climate during the school year actually affect the rate of learning?" The drops in academic achievement couldn't be explained by hotter weekends or hotter summers, but the trend was connected to higher temperatures on school days alone.

    The connection between lost learning and a greater number of hot days is one more example of how climate change is already affecting our lives-and it's an alarm bell for what we stand to lose in the future. Humans still have time to lessen the worst consequences of continued global warming. But unless significant changes occur in the next decade-which seem more and more unlikely—the world will be locked into an inescapable period of heat waves unlike our species has ever seen.