Can exercise during childhood protect you against memory loss many decades later?Exercise early in life seems to have lifelong benefits for the brain,in rats at least.

     “This is an animal study,but it shows that physical activity at a young age is very important—not just for physical development,but for the whole lifelong track of cognitive（认知的）development during ageing,”says Martin Wojtowicz of the University of Toronto,Canada.“In humans,it may delay the appearance of Alzheimer's symptoms（阿茨海默氏症）,possibly to the point of preventing them.”

    Wojtowicz's team divided 80 young male rats into two equal groups,and placed running wheels in the cages of one group for a period of six weeks.Around four months later—when the rats had reached middle age—the team taught all the rats to connect an electric shock with being in a specific.When placed in the box,they froze with fear.

    Two weeks later,the team tested the rats in three situations: exactly the same box in the same room,the same box with the room arranged differently,and a completely different box in a different room.

    The rats without access to a running wheel when they were young now froze the same percentage of times in each of these situations,suggesting they couldn't remember which one was dangerous.But those that had been able to run in their youth froze 40 to 50 percent less in both changed box settings.

    "The results suggest the amount of physical activity when we're young,at least for rats,has influence on brain and cognitive health—in the form of better memories—when we're older,"says Arthur Kramer of Northeastern University in Boston,who has found that,in humans,exercise promotes the growth of new brain cells.

    Have you ever noticed tiny raised areas on the branches of a tree? These may have been insects. These small insects feed on tree sap (汁液). Insects on urban trees are notably more abundant than those on rural trees. As a result, urban trees suffer from heavy infestations (害虫横行), and are often unhealthy or die. To protect and restore urban trees' health, we need to determine the factors that make these tree pests more successful in urban habitats.

    Living organisms interact closely with their environment. The warmer, more drought-stressed trees harbor more successful pests than cooler, less drought-stressed trees. As cities and natural habitats become hotter and drier, damaging insects will become more abundant on urban trees.

    Trees within urban forests are valuable economically and for the environmental sustainability (可持续性) of the region. More than half of the world's population lives in cities. Across the globe, people are moving into cities at a faster rate than ever. Rapid growth may turn cities into places with harder conditions. Although cities are primarily made of buildings, roads, parking lots, and vehicles, there are still plants in them. The trees within a city are referred to as the urban forest. Urban forests offer very big benefits to human and environmental health. They improve air and water quality, provide habitat for wildlife, cool down temperatures and beautify our environment. They make cities livable.

    However, being a city tree is not easy. Heat released by human activities is trapped in cities. As a result, temperatures in urban areas are often warmer than their surrounding rural areas. We call this urban warming or the urban heat island effect. Urban habitats are mostly made of surfaces of asphalt (沥青) and concrete. These surfaces reduce the amount of rainwater that reaches tree roots. As a result, urban forests may suffer, which can negatively affect people and the environment.

    What can we do to restore urban forests? Regular irrigation when possible may help keep pest populations under control. Planting tree species that are suitable to handle heat and drought stress would also reduce the occurrence of insect pest outbreaks.

    Membership

    All you need to do is fill out the order form at the bottom of the page, select your first order from our book list and then post the completed form back to us.

    Special offers for new members

    As a special offer, you may choose any reduced-price books from our new members' book list, to the value of 100 yuan in total. Tick the box on your form to order a free watch. Join before the end of this month and you receive another free book carefully chosen by our staff. Order an audio-book from the many on offer, at half the recommended retail price.

    When you've joined

    As a member you get around 50% off the publisher's price of every book you buy, and what's more, they come straight to your door. Your free club magazine arrives once a month to keep you up to date with the latest best-sellers we've added to our list. On the Internet, you can find all our titles for the year at our exclusive members' website. Our website also has a book swap service where members can request or offer books for exchange.

    Being a member

    All you have to do is order four books during your first year. After that, you can decide on the number of books you wish to take. In each of your monthly club magazines, our experienced staff choose a "Book of the Month" for you, which is offered at an extra-special price. If you do not want this book, just say so in the space provided on the form and send it back to us. We always send the book if we do not receive this form.

    Once we receive your order, your books are delivered within one week. And remember, you have up to a fortnight to decide if you wish to keep the books you have ordered. If they aren't what you expected just end them back!

    Red leaves are a symbol of autumn. Enjoying red leaves in the clear, refreshing autumn weather is indeed a good choice.

    Now let's have a look at the best red leaves around China and the beauty of autumn.

    Destination 1

    With different red colors, the Red Leaf Valley extends (延伸) more than 50 kilometers from Jiefang village in Qingling town to Yanjiang village in Songjiang town, Jilin province, Northeast China. Leaves are like different red pigments (颜料), including Chinese red, orange red, ruby red and bright red.

    Best time: October

    Destination 2

    Tachuan or Tashang village is in Huangshan city, Anhui province, East China. The beautiful autumn scenery there is known as one of the four best in China. The red leaves and clear spring add beauty to traditional houses, offering material for photography lovers.

    Best time: early to late November

    Destination 3

    As a result of low temperatures, maple leaves in areas south of the Yangtze River are like shy girls, gradually showing their beauty, turning from green to gold, gold to orange and finally to red. And as it changes slowly, different colors can be seen on the same trees called "colorful maple trees". Viewing at the mountainside is the best choice.

    Best time: October to November

    Destination 4

    For Guangdong province in South China, autumn always comes a little late and lasts longer. Through the end of January, you can see the red leaves any time you want. If you feel pity at saying good-bye to red leaves in North China, you can head to South China to view the beautiful scenery again.

    Best time: end of November to end of January

Notice for Tourists to Beijing Expo 2019

    The 2019 Beijing Horticultural Expo (园博会) from April 29 to October 7 is an opportunity for international discovery, where cultural elements of different places in China are on display, as well as gardens and buildings about each country's wonderful culture and history. Here is a notice for whoever plans to come.

    Quick Entry by Showing ID Cards.

    To make sure your quick and orderly entry into the Expo Site, please wait in lines and get your ID card ready for pre-check, ticket check and security inspection before entering. During the ticket check, those who hold discounted tickets must provide the materials about discount.

    Safe Tour to the Expo.

    Considering your personal safety, please don't take anything that may disturb other visitors or the order of the Expo Site, such as pets, kites, and speakers. Except for wheelchairs for the elderly and the disabled and strollers (婴儿推车)for children, no vehicles(机动车辆)are allowed to enter the Expo Site.

    Taking Action to Protect the Environment.

    To create a green, beautiful environment for yourself and others, please follow the travel rules, protect public buildings, keep environment clean and care plants growing in the Expo Site. Behaviors such as climbing or destroying structures and exhibits are not permitted.

    Orderly Travel by Limiting the Number.

    For the safety of visitors, sometimes staff members may limit the number of tourists into some gardens and buildings in the event of overcrowding Thank you for your understanding.

    Enjoying Service and Having Fun.

    Tourist service centers in the Expo Site provide services including information inquiry (查询) storage of personal belongings, wheelchair and stroller renting, lost found service, and search for missing persons. We hope you have a good time at the Expo.

    You can call the service hotline at 86-10-86484017 for inquiry, suggestion or complaint. Thanks for your attention.

A short period of sleep taken during the day is known as a nap. Naps don't just have benefits for adults at work, though. They could also help pupils to make the most of their school day. Studies have shown that a 20 to 30-minute "beauty sleep" makes people more alert and focused. This improves people's ability to remember new information, which would help school children concentrate during lessons. Experts say that napping also improves brain functions, such as memory and the ability to complete difficult tasks.

The school day starts early, which means that pupils don't always get enough sleep because there's no chance to have a lie-in（睡懒觉. Adding naptime during the school day would help exhausted pupils to make up for any sleep they've lost from getting up so early.

There are long-term benefits to taking a short nap, too. According to a recent study from University College London, the brains of people who have regular naps are bigger than those who don't. People's brains naturally shrink (萎缩）when they grow old, and the results showed that little sleeps can help people's brains to age more slowly.

Although a nap can seem like a good idea, going to sleep for too long can actually make you feel worse. It's not very pleasant to wake up from a daytime nap feeling confused and sleepy. Napping during the day can also have a negative impact on how well you sleep at night. This can create a cycle of not being able to sleep well at night, leaving you feeling even more tired in the daytime. Sleep expert Dr Clete Kushida said, "It's generally recommended to maximize(最大化） sleep at night."

Another consideration is that there really isn't time in the school day for pupils to go to sleep. Some parents and teachers are concerned that it would cause children to miss too much lesson time. Pupils might take advantage of the system and use their need for a nap as an excuse to get out of lessons.

So, what do you think? Should school allow kids to have naps, or should you wait until the evening to catch up on your sleep?