I was in my first year of college, making friends and enjoying life, but then my whole world turned upside down. I had a heart attack. It felt like someone was stabbing (刺) me in the chest with a knife over and over again.

    After three months of rest I went back to college, but then things took a turn for the worse. I was staying at my Nana's house and woke up in the middle of the night with a terrible pain in my chest. I knew I was having a heart attack again.

    I couldn't even shout for help. Luckily my grandpa was going to the toilet and heard me falling out of bed. If it wasn't for him, I probably wouldn't be here.

    The two holes in my heart were causing the problems and I needed an operation immediately to repair them. Unfortunately, the surgery didn't go well and they only managed to repair one of the holes.

    When I woke up from the operation, I had a really dry mouth and couldn't wait to have something to eat and drink. The biggest shock of all came when I was told that I needed a heart transplant and was put on the register. The doctors were stunned at how quickly heart failure came on – it usually takes years, but it took my heart less than six months to get to that stage. My whole world came crashing down, but I stayed strong. It was a choice between crying every day and getting on with my life.

    As time went on, life became even harder. I hated feeling weak all the time and needing help with everything. It got to the point where I thought I would never get a new heart. I was diagnosed with depression.

    Even though I thought that Christmas 2008 would be my last, I really enjoyed it and even had a good New Year. Everyone was crying for me when the clock struck midnight and they told me to keep fighting.

    A week later, I got a call from the doctors saying they'd found a suitable donor (捐赠人). My wish came true and thankfully the operation went well. I spent four hours in surgery where they took out my old heart and put a new one in. When I woke up I burst out crying. I had a second chance at life.

    It has long been thought that elephants rely on their large ears and bathing in rivers to stay cool in hot climates. New research, however, has showed that the world's largest land animals have a secret trick of controlling their body temperatures.

    Scientists have long been puzzled by temperature regulation(调节)in elephants. Generally, animals with large bodies tend to hold more heat because, compared to their size, they have a small surface area for heat to escape from. Elephants, with their heavy­weight frames, would appear to be at a disadvantage in the heat of their African and Asian habitats, especially because they have thick fur to protect them from bushes and trees.

    Scientists thought that these creatures, which weigh up to 13 tons when fully­grown, grow large ears to help them stay cool. The skin on the ears is thinner, so blood which flows into them cools down more easily. But findings by researchers at two universities in Vienna have showed that elephants are also able to cool down by increasing the blood flow to skin patches(斑) in other parts of their bodies.

    The researchers studied six African elephants at Vienna Zoo as they moved between outdoor and indoor environments to see how the temperature on their skin surface would change. They found up to 15 “hot spots” all over an elephant's body surface, in addition to large patches on the ears. The study shows how these patches expand as the air temperature increases and more blood flows nearer to the skin surface. Other experiments show that elephants in the wild use the same “windows” to control their body temperature.

    Elephants have two additional ways to stay cool: flapping(拍打)the ears and bathing. Together with these tricks, the skin hot spots allow the animals to keep their body temperature always at about 36 degrees—one degree less than humans'.

    Dogs were living as companions to the early settlers of North America over 10,000 years ago. The oldest domestic dogs in the Americas were thought to be around 9500 years old. Angela Perri of Durham University, UK, and her colleagues have carried out fresh radiocarbon dating on the two dog skeletons that gave this date, discovered in the prehistoric Koster site in Illinois, and found they were even older: around 10,100 years old.

    A third dog from another Illinois site called Stilwell II was older still, at 10,190 years old. That makes it the oldest known domesticated dog in the Americas. The team concluded that all three dogs were domesticated as they skeletons were complete and unskinned, and so hadn't been butchered for food. They had also been carefully buried, evidence they were valued by their owners. The Stilwell II dog, which probably resembled a small English settler, was under what seemed to be the floor of a living area. It is unclear why it took so long for tame dogs to arrive in the Americas, given that they were domesticated at least 14,000 years ago in Eurasia. By this time, people were already moving into North America from Siberia; there is evidence some reached Chile 18,500 years ago. Geneticists have found signs of at least three waves of migration over the following millennia. There is no evidence that domestic dogs accompanied them. “We don't know if dogs were part of the first waves of immigration to the Americas" says Luc Janssens of Ghent University in Belgium. "It could be so, but no archaeological bones have yet been found." It is "overwhelmingly probable" that some of the early settlers did bring dogs to the Americas, but they may not have had "the time or the spiritual compulsion to bury them", says Pat Shipman of Pennsylvania State University.

    Cropping (修剪) an Image With the Snap Shot Program

    Welcome to the world of photo-editing!

    Cropping an image allows you to zero in on (对准，聚焦) just the portion that is important to your project. For example, you may want to insert an image of a covered train in a report but may not want to include the whole train. Cropping the image allows you to select only the small area you wish to retain (保留) and eliminate all other portions of the original picture.

    Option 1: Cropping by Placing the Image in a Shape

    Screen Shot 1

    Using one of Snap Shot's standard shapes as a photo-editing tool requires no special abilities to crop an image with a standard shape:

    a. Click Cropping & Orientation from the Effects menu.

    b. Click to select one of the six shapes to frame your image.

    c. Use the mouse pointer to draw a frame around the portion of the image you wish to retain. Re-size the frame by dragging the shape's sizing handles. When you are satisfied with the results, click Cut It.

    d. Snap Shot will automatically return to the project that is open. (You may also copy or cut the cropped image and paste it into another application.)

    Option 2: Freehand Cropping of an Image

    Screen Shot 2

    If you want to trace the shape of an object in order to crop out everything else, freehand cropping is the way to go. To crop an image freehand:

    a. Click Freehand Crop from the Cropping & Orientation option on the Effects menu.

    b. Using the mouse pointer, trace around the shape you want to crop. Be sure to completely enclose the image by ending at the same place you began outlining.

    c. Click Cut It. Snap Shot will automatically return to the project that is open.

    Millions of Americans are living in areas at high-risk of river flooding, many of whom are completely unaware of the danger.

    While the risk of coastal flooding from extreme storms and rising seas rightly attracts plenty of attention, Americans are being urged to look inland for a similar threat receiving far less recognition: river flooding. New research conducted by the University of Bristol has shown that as many as 41 million Americans are highly at risk from river floods – more than three times the number previously estimated – with real estate (住宅区) in areas such as Louisiana, Florida, Arizona and West Virginia found to be especially at threat.

    For the first time, it has been possible to produce super quality flood risk maps that cover the whole United States, while previous Federal Emergency Management Agency (FEMA) flood maps cover no more than 60 per cent of the country. The fine details provided by these new maps also makes it possible to predict the powerful effects of flooding on many smaller streams than before, thus raising concerns about the increasing number of people potentially threatened.

    "We were all surprised by how many Americans we find are exposed to flooding from rivers," says Oliver Wing, from the University of Bristol's School of Geographical Sciences. "It's particularly worrisome considering that most of these people aren't even aware of the risk they face."

    Additionally, there is the possibility that this lack of awareness means construction in high-risk river flooding areas will continue to rise, despite the threats. Estimates (估量) suggest that projected population growth, continued urbanization trends (城市化趋势), and the unpredictable threats caused by climate change will leave over 60 million Americans vulnerable (易受攻击的) to a 100-year flood by the middle of the century. 'All of this highlights the urgent need for large areas of floodplain and flood risk management planning,' adds Wing.

Chinese President Xi Jinping once said. "Heroes come from the people." Every year, there are ordinary people spreading positive energy (正能量) and touching our hearts. Let's take a look at some of them.