My school stood in a big square playground in southeastern South Dakota. One teacher taught all grades, first through eighth. Most grades had only two or three students.

    Our school day started with the flag pledge(宣誓). Then the teacher called one grade at a time to the recitation bench beside her desk. She'd check our work, explain the new lesson, and dismiss us to go back to our own desks and do our new work, all in less than ten minutes per grade.

    At noon we ate lunches we had brought. Our lunches consisted of homemade sandwiches and if we were lucky, dessert. My favorite dessert was a fresh pear, and a piece of Mom's delicious sour cream chocolate cake.

    The annual Christmas program was the most exciting part of the year. We hurried through our lessons during December to allow time to practise poems, songs, and plays.

    A few days before the performance, the school board members borrowed equipment from the town and set up a stage across one side of the classroom. We hung bed sheets for curtains.

    On the evening of the performance, petrol lanterns hanging along the walls cast a warm, though not very bright, light over the gathering crowd. We could hardly contain our excitement as we looked from behind the curtains to wave at our parents.

    On a spring Sunday in a new term, just before the last day of the school term, everyone in the neighborhood gathered for a picnic. Our moms set fried chicken, bowls of salads, and desserts on the teacher's desk and the library table. After the dinner, we played games. One of the school board members brought big buckets of ice cream in the afternoon to top off the picnic. How we looked forward to that treat!

    I was just nineteen years old when I started my first teaching position in a country school with thirteen students. I felt excited, nervous and happy as I prepared my lunch bucket the first morning of the term. I can't remember what kind of sandwiches I packed, but I do remember I put in a fresh pear and a piece of chocolate cake for dessert!

    Anger often makes us uncomfortable. When you find your anger too uncomfortable to process, please let it go. But remember to create a healthy anger in your children is to practice creating a healthy anger in yourself. Once you're better at experiencing anger and expressing it in a healthy way, you'll be able to model a good style of anger for your kids.

    Some kids deal with anger by creating a "false self": a child who is perfect for their parents. People who have developed a false self are often passive aggressive and seem shallow because they've hid away all the feelings with depth and character.

    How do we keep kids from creating false selves? We need to raise them in an environment where it's safe to express feelings. Once you feel more comfortable with your own anger, you can teach your children why anger is a helpful emotion. When your kid expresses anger, help them examine what it is that has made them angry. Why did it make them angry? How did it do that? Then, you can teach them that while emotions are never wrong and are always valid, our expressions of our emotions are within our control.

    People who are afraid of their own anger will never learn how to listen to what their anger is trying to tell them. Instead of teaching our kids that their anger is wrong, that "happy families" are never angry, or that all feelings of anger lead to violence and fear, we can teach our children that anger is OK. Anger is natural, it is normal, and it can be experienced and expressed in a healthy way.

    Mountaineers have noted that as they climb, for example, up to the 12,633­foot Humphreys Peak in Arizona, plant life changes greatly. In the Sonoran Desert, one climbs into a pine forest at 7,000 feet and a treeless tundra(冻土带) on the top of the mountain. It may seem that plants at a given altitude are associated in what can be called “communities” －groupings of species. The idea is that over time, plants that require particular climate and soil conditions come to live in the same places, and are frequently to be found together. Scientists study the history of plant life and build up a picture of how groups of plants have responded to climate changes and how ecosystems develop. But are these associations, which are real in the present, permanent?

    A great natural experiment took place on this planet between 25,000 and 10,000 years ago, when small changes in the earth's orbit caused great sheets of ice to spread from poles. These glaciers(冰川) covered much of North America and Europe to depths of up to two miles, and then, as the climate warmed, they retreated. During this retreat, they left behind newly uncovered land for living things to occupy, and as those living things moved in they laid down a record we can read now. As the ice retreated and plants started to grow near a lake, they release pollen(花粉). Some would fall into the lake, sink to the bottom and mix with the sand. By drilling into the lake bottom it is possible to read the record of the plant life around the lake. The fossil record seems clear; there is little or no evidence that entire groups of plants moved north together. Things that lived together in the past don't live together now, and things that live together now didn't live together in the past. Each individual living things moved at its own pace. The fossil record seems to be telling us that we should be thinking about preserving species by giving them room to move about－to respond to environmental changes.

    Life in the Clear

    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet—as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, “These animals live through their life alone. They never touch anything unless they're eating it, or unless something is eating them.”

    And they are as clear as glass. How does an animal become see-through? It's trickier than you might think.

    The objects around you are visible because they interact with light. Light typically travels in a straight line. But some materials slow and scatter(散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks. Both scattering and absorption make an object look different from other objects around it, so you can see it easily.

But a transparent object doesn't absorb or scatter light, at least not very much, Light can pass through it without bending or stopping. That means a transparent object doesn't look very different from the surrounding air or water. You don't see it —-you see the things behind it.

    To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments(色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

Animals are built of many different materials—-skin, fat, and more—-and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat. Without much tissue to scatter light, it is easier to be see—through. Others build a large, clear mass of non-living jelly-lie(果冻状的)material and spread themselves over it .

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process. When they die, they turn a non-transparent milky white.

    CHICAGO -- New research on vegetables and aging gives mothers another reason to say "I told you so." It is found that eating vegetables appears to help keep the brain young and may slow the mental decline（下降） sometimes associated with growing old.

    On measures of mental sharpness, older people who ate more than two servings of vegetables daily appeared about five years younger at the end of the six-year study than those who ate few or no vegetables.

    The research in almost 2,000 Chicago-area men and women doesn't prove that vegetables reduce mental decline, but it adds to mounting evidence pointing in that direction. The findings also echo（回应） previous research in women only.

    Green leafy vegetables including spinach（菠菜）, kale and collards （甘蓝） appeared to be the most beneficial. The researchers said that may be because they contain healthy amounts of vitamin E, an antioxidant（抗氧化剂） that is believed to help fight chemicals produced by the body that can damage cells.

    Vegetables generally contain more vitamin E than fruits, which were not linked with slowed mental decline in the study. Vegetables also are often eaten with healthy fats such as salad oils, which help the body absorb vitamin E and other antioxidants, said lead author Martha Clare Morris, a researcher at the Rush Institute for Healthy Aging at Chicago's Rush University Medical Center.

    The fats from healthy oils can help keep cholesterol（胆固醇）low and arteries （动脉）clear, which both contribute to brain health. The study was published in this week's issue of the journal Neurology and funded with grants from the National Institute on Aging.

    The lower East Side is neither rich nor beautiful, but it can be a good place to shop.

    On Sundays, its streets are crowded with visitors and shoppers like these. They are trying to find a coat or a pair of shoes at a good price.

    Most people prefer to shop in the big department stores like Macy's, Gimbel's, or Bloomingdale's because there they can find clothing, furniture, toys, and food in one store.

    Some people like the smaller stores of Greenwich Village or other areas when they are looking for an unusual present.

    Some streets have only one kind of stores. Bracelets (手镯) and rings shine in the windows of Canal Street, and wedding dresses fill the stores of Grant Street. There are streets for furs(皮大衣), and, in one area, there are 600 shops for antiques (古玩)! Fifth Avenue is the most famous place to shop, and it is usually the most expensive. There you can find the latest styles from Paris, Italy, or New York. You can spend thousands of dollars on Fifth Avenue, or you can just window shop and admire the sights for free.