If you can find a tree which has been cut down，you will see many rings，or circles，on the base of the trunk.By learning to read these rings，you can find out about the tree's life.

    The number of rings tells you how old the tree is.Each year，new wood is formed on the outside of the tree.This new wood is light in color when the tree is growing in spring and summer，and dark in winter when the tree is not growing much.So，if you count the rings of dark­or­light colored wood，you can often find out how old the tree is.

    You can also tell which years have been good years and which years have been bad years.When the light­colored rings are very wide，it means that the tree has been growing quickly that year.If the rings are narrow，it has been growing slowly.If the rings on a tree trunk were greatly magnified，you would be able to see why the rings are light­colored when the tree is growing quickly and dark­colored when the tree is growing slowly.The tree trunk is made up of microscopic tubes，like some pipes，carrying water from the soil，through the trunk，and up to the leaves.They are wide and thin­walled when the tree is growing quickly and they are carrying a lot of water.They are narrow and stuck together when the tree is not growing so quickly.

    When a tree is old，the tubes in the centre of the tree don't carry water.The walls of the tubes have become thick with materials which have stuck along them over the years，forming a kind of wood called“heartwood”．This kind of wood is darker in color than the young，growing wood on the outside of the tree.

    You don't very often see whole tree trunks which have been cut across.But once you learn to read a cross section of the wood，you can see much more in wood which has been used to make boxes，houses and other things.

    In most wood，instead of seeing the trunk cut across，you are seeing it cut along its length.Because you don't see the whole tree，you can't tell how old it is.

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    Recently, online hike-sharing has become the new favorite in China. In major cities, bikes in, yellow, orange, blue, white and green, can be seen almost everywhere on the street. It seems that these bikes appeared suddenly, adding a new beautiful scenery to Chinese cities.

    Both the market and the public welcome online bike-sharing, but is it really a promising business? Well, it depends. After all, online bike-sharing platforms can never get away with huge operating cost and uncertain government policy.

    Some theorists might say that online bike-sharing platforms can earn a fortune simply through deposit. Since users will always need to rent bikes, their deposit will always be kept to online bike-sharing platforms.

    However，although online bike-sharing platforms may be able to use the deposit for other purposes at the primary stage, they will have to set up a special account, so that the deposit shall be used specially for its designated (指定的) purpose. As the market gets increasingly mature, they will have to do so whether to be responsible for users or in consideration of possible government regulations.

    Now that online hike-sharing platforms can，t make profit through deposit，how can they become profitable as fiercer market unfolds? Although Hu Weiwei, CEO of Mobike, stated in an article that she would take Mobike as charitable(慈善的) project if she failed, running a startup is absolutely different from managing a charity organization. After all , she has to pay back investors' billions of investment(投资).

    To make profit, online bike-sharing platforms might have toincrease rent fee for each trip, just as Didi did

    From this aspect, it might be a really good business. If we consider full screen ads fee, recommendation fee for business owners, etc. , its annual income might reach at least RMB 15 billion. If we consider the huge operation cost, including bike repairs，bikes' service life and labor cost, there might not be much net profit left. After all, offline operation cost has always been an unbearable burden for such internet plus mode-based startups.

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    Imagine the tallest building in the United States. Fill that giant building 44 times with rotten fruits and vegetables. Now you know how much food Americans waste every year.

    It is hard to believe, right? About 133 billion pounds of food get thrown away. That's one-third of all the food we produce. And a lot of it is thrown away for one simple reason: It's ugly.

    The problem is that nature isn't perfect. Apples can get scarred (留下疤痕) by storms. Cucumbers grow in C shapes. Carrots change into unusual fork-like forms. Watermelons get too big to fit on a refrigerator shelf. These crazy-looking fruits and vegetables may taste great. But most grocery stores refuse to sell them. Store owners say people judge food by how it looks. No one wants a tomato that looks like a two-headed monster. But what if you could buy that tomato for half-price?

    A new movement is trying to make people see the “beauty” in ugly food. Some stores are selling ugly produce. It tastes the same. And you pay less for it because the food doesn't look perfect.

    Usually, the stores find a nicer word than “ugly”. A Canadian chain uses “naturally imperfect”. In some US stores, it's “misfit produce”. Whatever you call it, ugly food helps many people. Fanners get paid for food they were going to have to throw away. Shoppers get cheaper fruits and vegetables. The ugly-food movement will also help some of the 44 million Americans who don't have enough to eat. Many groups give the ugly produce to hungry people.

    So really, who cares if that carrot looks a little… ugly?

    Planning to get away? Think passport first

    If you're planning to get away from it all this year, you should think passport first. Checking you have a valid passport before you book your trip takes minutes but could save you the trouble and cost of not being able to go.

    Renewing (更新) your passport before it runs out

You can renew your passport up to 9 months before it can no longer be legally used. So take the time now and save the tears later.

    Applying for a passport for the first time

    Our eligibility (资格) checks mean that it takes a minimum of one week to issue (颁发) a passport. So make sure you don't leave it to the last minute, and apply in plenty of time.

    Help with your application is just around the corner

    Selected Post Office branches and Worldchoice travel agents offer a Check and Send service that helps you with your application. It's convenient and you should receive your passport within 2 weeks.

    If you need to apply for or renew a passport, you can either:

    Pick up a Passport Application Form at Selected Post Office branches and Worldchoice travel agents.

    Or call the Application Form Request line on 0901 4700 100 or visit www.passport.gov.uk

    If your need is urgent, call 0870 521 0410 for an appointment at one of our offices. We can't guarantee to see customers without an appointment.

    From 14th January a guaranteed same day (passport renewals only) or one week service will be available from passport public counters.

    Calls will be charged 60p per minute and the cost per call should not normally be more than 90p.

    Calls are charged at national rates.

    Why do we dream? It's a question researchers have been studying for years. Now new research suggests that some dreams may result from the brain's effort to keep learning, even as we sleep.

In a study in Boston,100 volunteers were trained for an hour on a maze(迷宫). They tried to find their way through the difficult puzzle as quickly as possible. Then half of the volunteers were allowed to sleep for 90 minutes. The other half stayed awake, reading or relaxing. The ones who slept were asked to describe their dreams when they woke up.

    After the rest, the volunteers were asked again to solve the maze. Those who hadn't slept showed no improvement or did even worse after the break. Sleepers who didn't report any maze­related dreams did better but showed only a little improvement. However, four nap­takers who reported dreaming about the maze showed a surprising improvement. They scored 10 times higher after sleeping and dreaming about the maze.

    Even though the number of dreamers was small, the researchers noted that the gap in learning between the dreamers and non­dreamers was so wide that the finding was significant(有意义的).

The dreamers had all performed poorly on the test before dreaming about it. That suggests that struggling with a task might be the trigger that leads the sleeping brain to focus on it and work on how to deal with it.

    "It's almost as if your brain is going through everything that happened today," Dr Stickgold, a scientist at Harvard Medical School, said. "The things you're obsessed(迷住) with are the ones that your brain forces you to continue to do with."

    For the first time, the World Health Organization has included Traditional Chinese Medicine (TCM) in its globally influential medical compendium(手册), according to an international science journal.

    An article published by Nature on Wednesday said that TCM will be included in the latest version of the International Classification of Diseases (ICD)set to be released next year. Starting from the 1800s, the ICD has been improved and published in a series of editions, reflecting the advances in health and medical science over time. It serves as the foundation for the identification of global health trends, and the international standard for diseases and health conditions.

    The latest ICD is based largely on the work of the International Classification of Traditional Medicine (ICTM) project's experts from around the world. These experts had been working on traditional medicine research and practices for years.

    China has been promoting the modernization of TCM and pushing for TCM to gain acceptance worldwide. Tu Youyou, a Chinese expert focusing on the scientific study of drugs and medicines, was awarded the Nobel Prize in Medicine in 2015 for her research in TCM. Her discovery has saved millions of lives in developing countries in South Asia, Africa and South America. TCM is sure to grow in popularity globally.

    Though the application of traditional Chinese medicine, acupuncture(针灸) and other traditional medical practices has been on the rise, there's still a shortage of global classification and terminology(术语) tools for traditional medicine, according to officials of the WHO.

    "The decision is to promote the safe and effective use of traditional medicine by regulating, researching and combining traditional medicine products, practitioners and practice into health systems, where appropriate," the WHO was quoted as saying by Nature.