Deserts are found where there is little rainfall or where rain for a whole year falls in only a few weeks' time. Ten inches of rain may be enough for many plants to survive if the rain is spread throughout the year. If it falls within one or two months and the rest of the year is dry, those plants may die and a desert may form.

    Sand begins as tiny pieces of rock that get smaller and smaller as wind and weather wear them down. Sand dunes (沙丘) are formed as winds move the sand across the desert. Bit by bit, the dunes grow over the years, always moving with the winds and changing the shape. Most of them are only a few feet tall, but they can grow to be several hundred feet high.

There is, however, much more to a desert than sand. In the deserts of the southwestern United States, cliffs (悬崖) and deep valleys were formed from thick mud that once lay under a sea more than millions of years ago. Over the centuries, the water dried up. Wind, sand, rain, heat and cold all wore away at the remaining rocks. The faces of the desert mountains are always changing –-very, very slowly —as these forces of nature continue to work on the rock.

    Most deserts have a surprising variety of life. There are plants, animals and insects that have adapted to life in the desert. During the heat of the day a visitor may see very few signs of living things, but as the air begins to cool in the evening, the desert comes to life. As the sun begins to rise again in the sky, the desert once again becomes quiet and lonely.

    Sometimes you'll hear people say that you can't love others until you love yourself. Sometimes you'll hear people say that you can't expect someone else to love you until you love yourself. Either way, you've got to love yourself first and this can be tricky. Sure we all know that we're the apple of our parents' eyes, and that our Grandmas think we're great talents and our Uncle Roberts think that we will go to the Olympics. But sometimes it's a lot harder to think such nice thoughts about ourselves. If you find that believing in yourself is a challenge, it is time you build a positive self-image and learn to love yourself.

    Self-image is your own mind's picture of yourself. This image includes the way you look, the way you act, the way you talk and the way you think. Interestingly, our self-images are often quite different from the images others hold about us. Unfortunately, most of these images are more negative than they should be. Thus changing the way you think about yourself is the key to changing your self-image and your whole world.

    The best way to defeat a passive self-image is to step back and decide to stress your success. That is, make a list if you need to, but write down all of the great things you do every day. Don't allow doubts to occur in it.

    It very well might be that you are experiencing a negative self-image because you can't move past one flaw or weakness that you see about yourself. Well, roll up your sleeves and make a change of it as your primary task. If you think you're silly because you aren't good at math, find a tutor. If you think you're weak because you can't run a mile, get to the track and practice. If you think you're dull because you don't wear the latest trends, buy a few new clothes. But remember, just because you think it doesn't mean it's true.

    The best way to get rid of a negative self-image is to realize that your image is far from objective, and to actively convince yourself of your positive qualities. Changing the way you think and working on those you need to improve will go a long way towards promoting a positive self-image. When you can pat yourself on the back, you'll know you're well on your way. Good luck!

    Here is a record of the discussion about AI (artificial intelligence) conducted by several scientists:

    Scientist A: I would say that we are quite a long way off developing the AI, though I do think it will happen within the next thirty or forty years. We will probably remain in control of technology and it will help us solve many of the world's problems. However, no one really knows what will happen if machines become more intelligent than humans. They may help us, ignore us or destroy us. I tend to believe AI will have a positive influence on our future lives, but whether that is true will be partly up to us.

    Scientist B: I have to admit that the potential consequences of creating something that can match or go beyond human intelligence frighten me. Even now, scientists are teaching computers how to learn on their own. At some point in the near future, their intelligence may well take off and develop at an ever-increasing speed. Human beings evolve biologically very slowly and we would be quickly substituted. In the short term, there is the danger that robots will take over millions of human jobs, creating a large underclass of unemployed people. This could mean large-scale poverty and social unrest. In the long term machines might decide the world would be better without humans.

    Scientist C: I'm a member of the Campaign to Stop Killer Robots. Forget the movie image of a terrifying Terminator stamping on human skulls and think of what's happening right now: military machines like drones, gun turrets and sentry robots are already being used to kill with very little human input. The next step will be autonomous “murderbots” following orders but finally deciding who to kill on their own. It seems clear to me that this would be extremely dangerous for humans. We need to be very cautious indeed about what we ask machines to do.

    An idea that started in Seattle's public library has spread throughout America. The concept is simple: help to build a sense of community (社区) in a city by getting everyone to read the same book at the same time.

    In addition to encouraging reading as a pursuit (追求) to be enjoyed by all, the program allows strangers to communicate by discussing the book on the bus, as well as encouraging reading as an experience to be shared in families and schools. The idea came from Seattle librarian Nancy Pearl who launched the “If All of Seattle Read the Same Book” project in 1998. Her original program used author visits, study guides and book discussion groups to bring people together with a book, but the idea has since expanded to many other American cities, and even to Hong Kong.

    In Chicago, the mayor (市长) appeared on television to announce the choice of To Kill a Mockingbird as the first book in the “One Book, One Chicago” program. As a result, reading clubs and neighborhood groups sprang up around the city. Across the US, stories emerged of parents and children reading to each other at night and strangers chatting away on the bus about plot and character.

    The only problem arose in New York, where local readers could not decide on one book to represent the huge and diverse population. This may show that the idea works best in medium-sized cities or large towns, where a greater sense of unity (一致) can be achieved. Or it may show that New Yorkers rather missed the point, putting all their energy and passion into the choice of the book rather than discussion about a book itself.

    Ultimately, as Nancy points out, the level of success is not measured by how many people read a book, but by how many people are enriched by the process, or have enjoyed speaking to someone with whom they would not otherwise have shared a word.

    The horse I'm riding is named Candy, which is appropriate, taking account of her love for eating. As we go our way down the mountain of Big Bend National Park, Texas, I'm sweating—half due to the hot weather, half due to an effort to stay on the horse. Candy, however, is relaxed and stops to eat cactuses (仙人掌) as she passes. She is used to the dusty trails through hills and canyons(大峡谷) and ignores my attempts to guide her away from her delicious food. Our ride becomes a battle of will, which Candy wins easily. I comfort myself by admiring the views across Big Bend's wide open spaces.

    Texas only national park, Big Bend, extends across 800,000 acres of the Chihuahuan Desert, in the deep southwest of the state right along the border with Mexico. It is named after the U-turn that the Rio Grande River makes here. It has seen a lot of fights. The Spanish, Anglo-American settles, Mexicans, and Apache and Comanche American Indians all fought to rule this place.

    Our group member, Mike, knows every corner of the park and describes it as “sort of a secret place”. Even some Texans don't know about Big Bend, he says. Other local people describe it as a forgotten national park. Compared with the almost five million travellers that descend on the Grand Canyon every year, only 30000 make it here.

    There are six of us in the riding group, all fairly inexperienced, led by tour guides, Linda and Janelle, who keep both us and the horses in line. We trek along the top of an 800-foot mountain, with wide-winged eagles flying beside us. The air is noiseless.

    The park is fantastic for hikes and has a variety of marked walking paths. The walk is a five-mile round trip. While the final stretch is rather steep, the views over giant canyons and plains are worth the effort.

    Morning Environmental Education Program

    A fun environmental based activity program for kids will be held in the mornings at Camp Hawk. Curriculum(课程) is designed to be interactive(互动的). Fees are $60 and includes lunch.

    Camp Hawk is open to children of abilities; however, daily participation(参加) requires that a child be able to stay with the group while outside on adventures, as well as to listen to and follow directions from the counselors(辅导员).

    Topics Include:

    Tuesday: Kids will build a space station with legos(儿童积木), and build their solar system with bottle caps.

    Wednesday: Kids will learn about the importance of the mangroves(红树) to the Florida Keys and other areas of the world. They'll take a field trip to explore life in the mangroves, and make their own mangrove poem.

    Thursday: Campers will learn about the bottle nosed dolphin and the types of sharks that live in the keys. This session will also take them out of the classroom to the Dolphin Connection observation area.

    Friday: This day is all about reptiles(爬行动物). Kids will learn about "The mixed up Chameleon" activities and art project, Reptile "hunt" fieldtrip, and making lizard bracelets.

    Saturday: Campers will learn about all of the creatures of Florida by taking a fieldtrip to observe dolphins, fish, birds, reptiles, sharks, and insects. Create their own animal, make their own aquarium and feed the tarpon at the harbor.