【推荐1】Many people tend to peel(削皮)fruit and vegetables when preparing them. But often, it’s not necessary.    1    What’s more, discarded(被丢弃的)fruit and vegetable peels cause climate change.

Fruit and vegetables are rich sources of vitamins, minerals, fiber and many phytochemicals that protect your cells from harm.    2    In 2017, the World Health Organization reported that around 3.9 million deaths a year worldwide were linked to people not eating enough fruit and vegetables.

Eating 400g of fruit and vegetables a day, as the WHO recommends, is difficult to achieve for many people. So could consuming fruit and vegetable peels help with this issue by adding important nutrients to people’s diets?    3    For example, nutritionally important amounts of vitamins, such as vitamin C, and minerals like iron and zinc, are found in the peel of root vegetables like wild carrots, sweet potatoes and white potatoes. And the US Department of Agriculture shows that unpeeled apples contain 15% more vitamin C than their peeled equivalents.

    4    According to the UN’s Food and Agriculture Organization, uneaten food, including peel, generates 8%—10% of the world’s greenhouse gas emissions. New Zealand alone reports an annual wastage of 13,658 tons of vegetable peels and 986 tons of fruit peels.

Given the nutrient content of peel and its contribution to food waste, why do people peel fruit and vegetables? Some must be peeled for different reasons. For example, their outer portions are uneatable, don’t taste nice, are hard to clean or cause harm. Also, peeling may be a necessary part of the recipe, for example, when making mashed potato(土豆泥).

Are you still confused about whether to peel fruit and vegetables?    5    

【推荐2】There’s no need to be ashamed about dozing off in class. It is actually a natural phenomenon. Studies have shown that people can only stay completely focused on something for a maximum of 10 minutes.     1     Dozing off during an important activity or event on a regular basis can develop into a habit that you might carry into other areas of your life.

Scientists have found that avoiding overeating before class is one of the most effective ways to beat class sleepiness. Most people have experienced “food coma (昏迷)” after eating a large meal. Eating too much results in a feeling of heaviness that uses up your energy. This happens because the body releases chemicals that signal drowsiness after eating.     2    

Carbohydrates (碳水化合物) release more serotonin (血清素) from the brain, which makes you feel good.     3     Basically, not all foods have the same impact on your body. While some foods can increase your energy, others can make you sleepy. Also, tasking your body with digesting a large meal is exhausting. Eating large portions — especially of unhealthy foods — will leave your body with little energy to use elsewhere.

    4     This gives your body the opportunity to digest smaller amounts of food at a time, leaving you feeling energized instead of tired after your meals.

Also, avoid heavy foods and choose healthy, balanced meals instead.     5     An example of a well-rounded breakfast to have before class would be a glass of milk, an egg and a salad containing at least three vegetables.

【推荐1】In stressful times, the art of making people laugh could help to relieve pressure. We all know that laughter is the best medicine.     1     It creates physical changes in your body that accelerate healing and protect you from harm. Scientists tell us that people who can laugh at their own misfortunes bounce back faster and stronger.

If you have trouble seeing the funny side of your own failures, then you might find some useful advice in the story of a friend of mine, who developed an unpleasant reaction to garlic for which his doctor prescribed (开处方) a short course of ointment (药膏) and suppositories (栓剂).

    2     After a few minutes, the chemist, standing at the far back of the shop, shouted at the top of her voice, “I’ve got your ointment, but I’ll have to order your suppositories!”

Following a short yet strongly uncomfortable silence, she came forwards to the counter and said, “    3    ” “Yes, you did,” was my friend’s quiet reply. I asked him how he was able to see the funny side of such an embarrassing incident and he said, “If I was standing in the shop and this had happened to someone else, it would have been funny.     4    ”

Laughing at yourself doesn’t make you a fool. It makes you strong, confident and self-assured. We all make mistakes; we all forget, trip, take wrong turns.     5     They cannot learn and will repeat the same mistakes, over and over again.

【推荐2】One key element of human language is semantics (语义). Scientists had long thought that unlike our words, animal vocalizations (发声) were involuntary, renecting the emotional state of the animal without conveying any other information. But over the last four decades, numerous studies have shown that various animals have distinct calls with specific meanings.

Many bird species use different alarm calls. Japanese tits, which nest in tree holes, have one call that causes their baby birds to get down to avoid being pulled out of the nest by crows, and another call for tree snakes that sends them jumping out of the nest entirely. Siberian jays vary their calls depending on whether an enemy is seen looking for food or actively attacking — and each call gets a different response from other nearby birds.

Two recent studies suggest that the order of some birds’ vocalizations may impact their meaning. Though the idea is still controversial, this could represent a basic form of the rules governing the order and combination of words and elements in human language known as syntax (句法), as illustrated by the classic “dog bites man” vs. “man bites dog” example.

Even if some birds share basic aspects of human language, we still know very little about what’s actually going on in their minds. Most animal communication research has focused on describing signals and behavior, which on the surface can look a lot like human behavior. Determining if the underlying cognitive (认知的) processes driving the behavior are also similar is much more challenging, as at the heart of this question is intentionality: Are animals merely reacting to their environment, or do they intend to convey information to one another?

【推荐2】Suzanne Simard, a professor of forest ecology who called herself a “forest detective”, was raised in mountains in Canada. Few scientists make much impact with their PhD thesis, but, in 1997, she did just that. Her research on the “wood wide web” made the cover of Nature and transformed our understanding of forests. What was then a challenge to traditional ideas is today widely accepted.

A mushroom is the part of a fungus (真菌) that sticks up above the ground. Thin, white threads grow from its stem deep into the soil. These threads are called hyphae (菌丝). Hyphae connect themselves to tree roots. They also stretch from root system to root system, like an underground network. This network may go for miles. Hyphae pick up nutrients and water from soil. The fungus threads that connect to tree roots share their nutrients and water with the trees. In return, they sip a bit of the sugar the trees make. Sharing helps both trees and mushrooms live. It’s also how trees communicate.

When a tree is being eaten by bugs, it makes chemicals to shoo them away, sort of like bug repellent (驱虫剂). The chemicals travel through the tree, down its roots, and into the hyphae network. Other trees connected to the network taste the chemicals. That tells them a nearby tree is under attack, so they start to make their own bug repellent. Trees do more than share warnings through the hyphae. They also help each other. In the fall, paper birch trees drop their leaves and can no longer make sugar. So, a fir tree that stays green all winter uses the network to send extra sugar to the birch until spring comes again. This system of sharing information and nutrients through the hyphae is sometimes called the “wood wide web”, because it works a bit like the Internet.

Local climate sets the stage for the wood wide web, researchers say. In cool temperature and boreal forests, where wood and organic matter decay slowly, network-building EM fungi rule. By contrast, in the warmer tropics where wood and organic matter decay quickly, AM fungi dominate. These fungi form smaller webs and do less intertree swapping, meaning the tropical wood wide web is likely more localized.

Ecologist Thomas Crowther’s results suggest that as the planet warms, about 10% of EM-associated trees could be replaced by AM-associated trees. Microbes in forests dominated by AM fungi deal with carbon-containing organic matter faster, so they could liberate lots of heat-trapping carbon dioxide quickly, potentially accelerating a climate change process that is already happening at a frightening pace.