Exercise may help to safeguard the mind against depression through previously unknown effects on working muscles, according to a new study involving mice.

    Mental health experts have long been aware that even mild, repeated stress can contribute to the development of depression and other mood disorders in animals and people. Scientists have also known that exercise seems to cushion against depression. But precisely how exercise, a physical activity can lessen someone's risk for depression, a mood state, has been mysterious. So for the new study, researchers at the Karolinska Institute in Stockholm studied the brains and behavior of mice in a complicated and novel fashion.

    We can't ask mice if they are feeling cheerful or in low spirits. Instead, researchers have pictured certain behaviors that indicate depression in mice. If animals lose weight, stop seeking out a sugar solution when it's available — because, probably, they no longer experience normal pleasures — or give up trying to escape from the cold-water zone just freeze in place, they are categorized as depressed. And in the new experiment, after five weeks of frequent but low-level stress, such as being lightly shocked, mice displayed exactly those behaviors. They became depressed.

    The scientists could then have tested whether exercise blunts (延缓) the risk of developing depression after stress by having mice run first. But, frankly, from earlier research, they wanted to know how, so they bred pre-exercised mice. A wealth of earlier research by these scientists and others had shown that aerobic exercise, in both mice and people, increases the production within muscles of an enzyme (酶) called PGC-1alpha. The Karolinska scientists suspected that this enzyme somehow creates conditions within the body that protect the brain against depression. Then, the scientists exposed the animals, which without exercising, were in high levels of PGC-1alpha to five weeks of mild stress. The mice responded with slight symptoms of worry. But they did not develop depression. They continued to seek out sugar and fought to get out of the cold-water zone. Their high levels of PGC-1alpha appeared to make them depression-resistant. Finally, to ensure that these findings are relevant to people, the researchers had a group of adult volunteers complete three weeks of frequent endurance training, consisting of 40 to 50 minutes of moderate cycling or jogging. The scientists conducted muscle biopsies (活体检查) before and after the program and found that by the end of the three weeks, the volunteers' muscle cells contained substantially more PGC-1alpha than at the study's start. The finding of these results, in the simplest terms, is that “you reduce the risk of getting depression when you exercise,” said Maria Lindskog, a researcher at the Karolinska Institute.

    The art of growing dwarf trees, or "bonsai"（盆景） as their Japanese planters call them, is increasing in popularity in the United States. Growing bonsai can make a fascinating hobby for anyone who enjoys plants and creating beautiful effects with them.{#blank#}1{#/blank#}．

    In growing bonsai, in fact, one must be careful in choosing the type of tree, as the growing conditions are unusual.{#blank#}2{#/blank#}．Varieties of pines with small needles and hardwood trunks are especially suitable.

    {#blank#}3{#/blank#}This is necessary because the major growth of bonsai is kept confined(被限制) to the tree's trunk and leaves, not its root system-a process quite unlike what is done with other plants.

    Another thing the bonsai-grower must do is to trim （修整） the roots and branches of the tree periodically （定期地）. Unless this is done, the plants will not have the proper proportions(比例) and will look unnatural.{#blank#}4{#/blank#}

    The last thing one must do is to be careful to keep the tree well-watered. Because bonsai are grown in smaller-than-usual containers, they often need more water than ordinary houseplants do.

    As can be seen from the above, the art of bonsai-growing is one which requires a certain amount of time and effort.{#blank#}5{#/blank#}Imagine having such a tree in your living room and passing it down through several generations of your family. That is exactly what bonsai-growing is all about: establishing a tradition of beauty which lasts for years and years and is a symbol of the beauties of the natural world.

    It was a weeknight. We were a half dozen guys in our late teens, hanging around “the flat” — as usual. The flat was poorly furnished, which, after some time, grew tiresome. We wanted action.

    We got in a car, big enough for all of us to crowd into — and off we went, in search of adventure. We soon found ourselves at Blue Gum Corner, a place named after the huge old blue gum tree that stood by there, a well-known local landmark. It stands at a minor crossroad leading to our town. The trunk is tall and smooth with no handholds for climbing. About six metres from the ground the first branch sticks out over the road. We parked beneath the huge old tree and discussed what we might do. All of a sudden we hit upon an idea — a hanging! I was chosen as “hangee”.

    The plan was quite simple. As I stood upon the roof of the car, the rope (绳子) was threaded down my jacket through my collar and down one leg of my jeans. I put my foot through the loop at the bottom. There I hung, still. The boys rolled about laughing until, a car, I hear a car! Before they ran to hide in the nearby field, they gave me a good push so that “the body” would swing as the car drove by.

    To our disappointment, the car simply turned off for town without even slowing. The boys came out of their hiding places and we discussed the situation. Surely they had seen me, hadn't they? Then we heard another car. The act was repeated, but still without any obvious reaction. We played the game about five or six times, but as no one seemed to notice, we abandoned the trick.

    What we did not know was that every car that had passed had unquestionably seen “the body” and each one, too scared to stop, had driven directly to the local Police Station. Now at that time of the night, the local policeman was sound asleep in his bed, so the first person sent to the scene was the traffic officer that happened to be on duty that particular night. He had been informed that some person had been killed, by hanging, at Blue Gum Corner. When he arrived, the body was gone! And he was hearing “unnatural sounds” from the surrounding area. As far as he knew, some fierce animal was hiding in the field before him, possibly dragging a body behind him — and we thought we were scared!

    He went to his radio and made a call that really began to worry us. I lay so close that I could hear every word. He called for the “armed police” and a “dog team, better make it two” and he had a “serious situation” at Blue Gum Corner. Then the police officer arrived. After a briefing from the traffic officer he decided not to go into the field until armed police and dog teams arrived. Now two spotlights were on the field and none of us could move.

    As luck would have it, police cars cannot leave their spotlights on all night without charging their batteries. So, after a time, the two officers began lightening the field by turns, allowing us the opportunity to move on our fours for freedom. One by one, we all managed to steal away and make our way home. Behind us we left what must have looked like a small city of lights, police cars, roadblocks, barking dogs, armed officers and an old rope hanging from a tree.

    When I think back to that night, to that tree, to what the drivers of the cars think happened, to what police believe happened, and to what I know happened, I am reminded of a simple truth — our eyes see darkness and light, color and movement, our ears hear only vibrations (振动) in the air. It is how we explain these vivid pictures that shapes our “reality”.

    As you grow rapidly through your teenage years, you will experience a lot of changes. The changes may seem difficult. {#blank#}1{#/blank#} Don't panic! You will deal successfully with them! You are a young adult now!

    With more responsibility, you will find more freedom to make your own choices. This is a time to be well informed about making choices. In this way you can make healthy balanced decisions. {#blank#}2{#/blank#}You may already know your career path or you may have no idea at all what you want to do. Both situations are fine! Work hard and the right opportunity will present itself to you.

    Young adulthood means greater freedom and more choices. {#blank#}3{#/blank#}But try not to shut your family out of your life. You should learn to think of others even though you are old enough to look after yourself.

    It is also perfectly natural at this time for you to spend more time with your friends than your family. {#blank#}4{#/blank#} A true friend will stand by you no matter what happens.

    This period is a part of the life cycle. There are some people who will be with you throughout life's journey. There will be some people with whom you part and go separate way. Leaving school can be hard. The reality is that you may not even see all of your classmates again.

    You are a young adult. It is your life. No one can live it for you. {#blank#}5{#/blank#} So making the right choices will be important to you. Life is for living. Enjoy your life wisely!

A. Choose your friends wisely

B. They will help shape the future

C. They may seem to happen quickly

D. You will probably want to be independent

E. You may appreciate what you have in your own life

F. The choices that you make from now on will be your choices

G. Your family has been with you since you came into this world

    I was deeply moved by the kindness of an elderly flower seller at Sydney's Central Station one evening.

    I was feeling as cold as the winter winds quickening the steps of the people who buried chins (下巴) in scarves and hands deep into coat pockets. In many ways, 2018 had proven an arduous year. My teenage daughter had left home for university, my job of 23 years was no more, and a creative project I'd given my all to for years had also been suddenly called off. I also found out a person I considered a friend was far from it.

    A year earlier, I'd dreamt about an earthquake. In the dream, a red light flashed inside a building and then the earth began to rock. Walls fell down on me as I ran into the open, feeling sorry for the people I hadn't loved enough. Before I was buried completely by the falling world, I shouted, "Abuelo, ayudame," in my native Spanish. "Grandfather, help me!"

    Now, with the very real aftershocks of a series of unexpected endings, I walked into a little flower shop to buy a gift for a friend. The gentleman at the shop looked at me and turned away for a moment, returning with a fragrant flower. "For you. You need to smile today," he said in a rich and beautiful accent, offering me the flower with eyes full of care. It took all my strength not to cry. Then he gave me a grandfatherly hug that made me want to tell him everything.

    Instead, I thanked him and headed for the train. How did he know? I wondered. For the first time in weeks, I felt hope.