It was a hot, humid day, and my brother Walt and I had decided that the only way to survive it would be to go swimming in a deep swimming hole across Mr. Blickez's pasture(牧场) and through some woods.

    The only problem with our plan was that this pasture was guarded by a huge, mean Hereford bull. Mr. Blickez had told us that Elsie was them eanest bull in the township, maybe even the county, and we believed him. But the hotter it got, the more we thought there was something doubtful about his claim. For one thing, we remembered Mr. Blickez liked telling tall tales; for another, Elsie seemed like an odd name for a bull.

    Finally, I talked Mom into asking permission for us to walk through the pasture, but then another problem surfaced. Mom said she would talk to Mr. Blickez if we would take our cousin Joanie along with us. Joanie was almost two years older than me and a head taller. If her teasing ever got around my grade school, it would be all over for me. In fact, I still had a headache from a quarrel with her that morning. “I'm not going swimming with that dumb girl cousin.” I told my mom.

  “Either Joanie goes with, or you stay home alone,” Mom said inher serious tone. I gave in and we set out. On our way across the pasture, Walt yelled suddenly. Elsie had approached him quietly and was licking(舔) his back. Joanie and I dove under the wire fence, but while I was on the ground I looked up and saw that Elsie wasn't a big mean bull after all. She was going to keep licking my brother's back as long as he stood still.

    We had many good days growing up and visiting our secret swimming hole guarded by the so-called “big mean bull”. And as it turned out, fora girl cousin, Joanie hasn't been too bad. She's been one of my best friendsover the years.

    You get anxious if there's no wifi in the hotel or mobile phone signal up the mountain. You feel upset if your phone is getting low on power and you secretly worry things will go wrong at work if you're not there. All these can be called “always on” stress caused by smart phone addiction(上瘾).

    For some people, smart phones have freed them from the nine-to-five work. Flexible working has given them more autonomy (自主权) in their working lives and enabled them to spend more time with their friends and families. For many others, though, smart phones have become cruel masters in their pockets, never allowing them to turn them off and relax.

    Pittsburgh-based developer Kevin Holesh was worried about how much he was ignoring his family and friends in favor of his iPhone. So he developed an app — Moment — to monitor his usage. The app enables users to see how much time they're spending on the device(设备) and set up warnings if the usage limits are broken. “Moment's goal is to promote balance in your life,” his website explains. “Some time on your phone, some time off it enjoying your loving family and friends around you.”

    Dr. Christine Grant, an occupational psychologist at Coventry University, said, “The effects of this ‘always on' culture are that your mind is never resting, and you're not giving your body time to recover, so you're always stressed. And the more tired and stressed we get, the more mistakes we make. Physical and mental health can suffer.”

    And as the number of connected smart phones is increasing, so is the amount of data. This is leading to a sort of decision paralysis (瘫痪) and is creating more stress in the workplace because people have to receive a broader range of data and communications which are often difficult to manage. “It actually makes it more difficult to make decisions and many do less because they're controlled by it all and feel they can never escape the office,” said Dr. Christine Grant.

    Rapid advances in a new technology will soon transform science fiction into reality — meaning people will have driverless cars, small robots at their command and the ability to experience being in another place without leaving home, predicted Google executive chairman Eric Schmidt at the Mobile World Congress in Barcelona, the planet's largest cell phone trade show.

    Introduction of books available online, Internet translation of languages and voice recognition for computers all happened much faster than anyone could foresee and that technological research into even more previously unheard of advances is progressing at a fast speed.

    “People who predict that holograms（全息图）and self-driving cars will become reality soon are absolutely right,” Schmidt told thousands of attendees. Research under way will lead to situations where people can put themselves at events like a rock concert so that they can see, hear and even feel the event. And turn down the volume, if it's too loud.

    One attendee said she was scared that the possibility could be dehumanizing, but Schmidt replied by holding up his cell phone into the air. “It has an off button and it is here on the right,” Schmidt said. “My point is that it is all about your control. If you don't like my version of a rock concert, I'm not forcing you to go.” In the future, small robots could be used so busy people can send them to events for video and voice transmissions when their presence isn't required, Schmidt said.

    Technology in the near future will redefine the relationship among people in the world. “With technology comes power and with power comes choice, and smarter resourceful citizens are going to demand a better deal for their new life,” Schmidt said.

    There might be as many as 10 million species of complex life on this planet today —— a huge number. But add up all of the complex species that ever lived and some biologists think the grand total would be about five billion. The estimate leads to an astonishing conclusion: a staggering 99% of species are not around any more. They have been driven to extinction.

    More species are joining the ranks of the extinct every year. Many scientists believe we are living through an episode of remarkably rapid extinction, on a scale that has been seen only five times in the last half a billion years.

    They call this current episode the sixth mass extinction —— a large, global decline in a wide variety of species over a relatively short period of time. And they tend to agree that humans are the main cause.

    Over-hunting, overfishing, and human-driven habitat loss are pushing many species to the brink. In fact, we have changed the planet so much that some geologists are now suggesting that we have entered a new phase in Earth's history; an epoch they call the ＂Anthropocene＂. By 2100, it is expected that humans will have caused the extinction of up to half of the world's current species.

    Because we are living through this extinction, it is relatively easy for us to study the driving forces behind it. But how do we determine what caused other mass die-offs that happened long ago? To do so we have to look at what archaeologists, palaeontologists, geologists and other scientists have concluded from the evidence they have gathered.

    The trouble is, those scientists do not always agree with one another —— even about the most recent extinction event. As well as the five-or six- mass extinctions, there have also been many smaller extinctions.

    One of these mini extinction events happened towards the end of the Pleistocene, a few tens of thousands of years ago. It is sometimes called the ＂megafaunal＂ extinction because many of the species it claimed were particularly large animals, weighing more than 97lb (44kg). However, its cause remains a debate amongst scientists.

    The city of San Francisco is a wonderful tourist attraction that offers many different things to see and do. The best way for a traveler to get a good look at the city is to take one of the many different tours there

    Walk to Tour the City

    When touring the city by walking, you aren't going to walk much. What's more, there are far more benefits. This kind of tour allows you to see as many buildings of the city as possible. A tour of the city on foot usually focuses on a more localized neighborhood level, which can be very interesting in a number of different ways.

    Hit the Waters of San Francisco Bay

    The waters of San Francisco Bay have played an important role in the city's development over the last century. Touring San Francisco from the water is completely unique way for you to see this wonderful city.

    Take a Bus Tour

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    Tour San Francisco From the Air

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    Plants are living things. So can they feel pain? Plants don't feel pain the same way animals and people do, says Anke Steppuhn. She is a scientist at the Free University of Berlin in Germany. "What we define as pain usually has to do with a nervous system," Steppuhn explains. When you put your hand too close to a hot stove, nerve cells send a signal to your brain. Your brain decodes (解码) that signal as pain. This causes you to pull your hand away before any serious damage is done.

    Plants don't have nerves or brains, so they can't feel pain like we do. "But plants do recognize when something is hurting them," Steppuhn says. Because they are rooted to the ground, they can't escape a dangerous situation. So they need other ways of fighting back.

    The biggest threat to a plant's life is getting eaten. Some plants grow sharp little hairs. Other plants produce bad-tasting or even harmful chemicals. These force an attacker to abandon its meal. A plant called bittersweet nightshade does something even smarter, Steppuhn found. When a slug (蛞蝓) chews holes in a nightshade' s leaf, liquid begins dripping (滴) around the wound. It is almost as if the plant were bleeding. The liquid is sugary nectar (花蜜), and it happens to be a favorite food of ants. In their effort to collect the nectar, the ants swarm (蜂拥而至) all over the injured plant. They will attack anything that stands in their way. That includes the slug that damaged the plant in the first place. It's a very clever trick. Whenever a slug attacks a plant, the plant calls an army of ants to kill the slug.

    Nectar isn't the only way plants attract bodyguards. They also release certain chemicals into the air when they are being eaten. People usually can't detect these smells. But wasps (黄蜂) can. When a wasp detects this cry for help, it races to the scene of the crime. If it finds the right kind of insect chewing down on the plant, the wasp will interrupt the attacker's meal. It will do this by laying eggs inside the insect's body!