Below is a selection from a popular science book.

    If blood is red, why are veins（静脉） blue?

    Actually, veins are not blue at all. They are more of a clear, yellowish color. Although blood looks red when it's outside the body, when it's sitting in the vein near the surface of the skin, it's more of a dark reddish purple color. At the right depth, these blood-filled veins reflect less red light than the surrounding skin, making them look blue by comparison.

    Which works harder, you heart or your brain?

    That kind of depends on whether you're busy thinking or busy exercising. Your heart works up to three times harder during exercise, and shifts enough blood over a lifetime to fill a supertanker. But in the long run, your brain probably tips it, because even when you're sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it.

    Why do teeth fall out, and why don't they grow back in grown-ups?

    Baby (or “milk”) teeth do not last long; they fall out to make bigger room for bigger, stronger adult teeth later on. Adult teeth fall our when they become damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you're done. When they're gone, they are gone. This is because nature figures you're set for life, and what controls regrowth of your teeth switches off.

    Do old people shrink as they age?

Yes and no. Many people do get shorter as they age. But, when they do, it isn't because they're shrinking all over. They lose height as their spine（脊柱） becomes shorter and more curved due to disuse and the effect of gravity(重力). Many (but not all) men and women do lose height as they get older. Men lose and average of 3-4 cm in height as they age, while women may lose 5 cm or more. If you live to be 200 years old, would you keep shrinking till you were, like 60 cm tall, like a little boy again? No, because old people don't really shrink! It is not that they are growing backwards —- their legs, arms and backbones getting shorter. When they do get shorter, it's because the spine has shortened a little. Or, more often, become more bent and curved.

    Why does spinning make you dizzy（眩晕的）?

    Because your brain gets confused between what you're seeing and what you're feeling. The brain senses that you're spinning using special gravity-and-motion-sensing organs in your inner ear, which work together with your eyes to keep your vision balance stable. But when you suddenly stop spinning the system goes out of control, and your brain thinks you'removing while you're not.

    Where do feelings and emotions come from?

Mostly from an ancient part of the brain called the limbic system. All mammals have this brain area —- from mice to dogs, cats, and humans. So all mammals feel basic emotions like fear, pain and pleasure. But since human feelings also involve other, newer bits of the brain, we feel more complex emotions than any other animal on this planet.

    If exercise wears you out, how can it be good for you?

    Because our bodies adapt to everything we do to them. And as far as your body is concerned, it's “use it, or lose it”! It's not that exercise makes you healthy, it's more that a lack of exercise leaves your body weak and easily affected by disease

    Four years ago, we asked ourselves: what if we could create a shopping experience with no waiting in lines and no checkout? Or could we create a physical store where customers could simply take what they want and go? Our answer to those questions is Amazon Go, where you could experience the idea of "just walk out shopping".

    Amazon Go is a new kind of store with no checkout required. We created the world's most advanced shopping technology, so you never have to wait in line. With our "just walk out shopping" experience, simply use the Amazon Go app to enter the store, take the products you want, and go! No lines, no checkout.

    Our checkout-free shopping experience is made possible by the same types of technologies used in self-driving cars: computer vision, sensor fusion, and deep learning. Our “ just walk out technology ” automatically detects when products are taken from or returned to the shelves and keeps track of them in your virtual cart. When you have done shopping, you can just leave the store. Shortly after, we'll charge your Amazon account and send you a receipt.

    We offer delicious ready-to-eat breakfast, lunch, dinner, and snack options made fresh every day by our on-site chefs and favorite local kitchens and bakeries. Our selection of food stuff ranges from bread and milk to cheeses and locally made chocolates. You'll find well-known brands we love, plus special finds we're excited to introduce to customers. For a quick home-cooked dinner, pick up one of our chef-designed Amazon Meal Kits, and you can make a meal for two in about 30 minutes.

    Our 1,800-square-foot shopping space is conveniently compact, so busy customers can get in and out fast. It is located at 2131, 7th Ave, Seattle, WA, on the corner of 7th Avenue and Blanchard Street. All you need is an Amazon account, a supported smart phone, and the free Amazon Go app.

    Amazon Go is currently only open to Amazon employees in our testing program, and will be open to the public soon.

    When a dog looks at you with big puppy-dog eyes, it's hard for you to go away, and you may speak out “Awww” without hesitation. However, there's a reason why you find a dogs stare so attractive. That sweet stare actually causes the release of a particular hormone, or chemical messenger in the body. This hormone creates feelings of affection in humans. The same thing happens to dogs when people look back at them. Scientists believe this helps people and their four-legged friends bond, or feel connected. Scientists have wondered what causes dogs to lovingly stare at their owners. To find out, a team of researchers from Azabu University in Japan studied 30 owners and their dogs.

    The researchers found that after the pets and their owners spent half an hour together, both showed a rise in oxytocin (催产素). One key role of this hormone in many animals is to promote bonding, like that between a mother and newborn. The increase of oxytocin didn't happen, though, when scientists repeated the experiment with wolves and the humans who had raised them.

    A second experiment also found that if dogs were given oxytocin, they looked at their owners longer. Scientists aren't sure exactly why, but this reaction occurred only with female dogs. Their owners oxytocin levels also rose as a result.

    The result of these experiments might help answer an age-old question: How did the fearsome wolf ancestor of modern dogs turn into man's best friend? Takefumi Kikusui, an animal scientist who worked on the study, thinks that the change happened when dogs first became domestic (驯养的).

    According to Kikusui, there may have been a small group of wild dogs that were naturally friendlier. “Humans are very sensitive to eye contact. By using this special communication tool, the dogs are able to win over our hearts. If they are more likely to make eye contact, it would be easier for them to bond with dog owners,” Kikusui said.

    In today's Internet age, the demand for online games continues to grow. Online computer game centers exist in many cities and towns throughout Asia. Facing the pressures of school and life, people tend to the virtual（虚拟的）world, expecting a diversion from these problems. Too often, however, they can lead to problems and unhealthy addictions.

    This is most clearly seen in the example of South Korea. The country has the world's highest percentage of high-speed Internet services. It also has a high number of online game players and related problems. In 2002, a young man collapsed(突然晕倒) and died while playing online games. He had been playing almost non-stop for 86 hours at an Internet café. Another young man killed his sister after becoming confused between the online world and real life. A 12-year-old boy stole US $ 16,000 from his father and ran away from home. He did this to continue his obsession(着迷) with an online game. Such problems, however, don't just happen in South Korea. They are spreading to other parts of Asia as well.

    What kinds of people develop online game addiction? What does the problem look like? Dr. SueHuei Chen, a clinical psychologist, researches Internet addiction. She discovered some signs of at-risk individuals such as lack friendships and good social skills. Those problem individuals feel it so compulsive（强迫的）to play online games that they could sacrifice things such as school or family. They feel the need to spend more and more time online. And they become upset if anyone tries to limit their online game playing.

    How many problem game players are there? In mainland China, the potential number of problem online gamers is alarming. In 2004, the China daily reported that China had 13.8 million online game players. Besides, it stated that 80 percent of these were under 25 and had signs of addiction. Such numbers point toward a growing problem among Chinese youth.

    Make sure to keep control over your online game playing. If you don't control it, it can get control of you.

    HOLLAND & BARRETT

    Valerian capsules

    A traditional herbal medicinal product used for the temporary relief of symptoms of mild anxiety and to aid sleep. This is based on traditional use only.

    Active Ingredients:

    Each capsule contains 337mg of extract (as dry extract) from Valerian root (Valerian officinalis L) (equivalent to 1683mg-2020mg of Valerian root).

    Dosage（剂量）:

    For oral use only.

    For adults and elderly:

    Mild anxiety — Take 1 capsule 3 times daily.

    To aid sleep — Take 1 capsule 30 minutes to 1 hour before bedtime with an earlier dose during the evening if necessary.

    Swallow the capsule with water. As the effects of this product may not occur immediately, the capsule should be taken continuously for 2-4 weeks.

    Duration of use: If symptoms worsen or do not improve after 4 weeks, a doctor or a qualified healthcare practitioner should be consulted.

    Warnings:

    Do not exceed the stated dose.

    Do not take this product if you are:

    a. Under 18 years of age

    b. Pregnant or breastfeeding

    c. Allergic to Valerian or any of the excipients in this product

    d. Already taking a medicine for sleep or anxiety

    Storage:

    Store the capsules below 25℃.

    Keep the bottle tightly closed.

    Keep out of sight and reach of children.

    Registration Holder:

    NBTY Europe Limited, Samuel Ryder House, Barling Way, Nuneaton, Warwickshire, CV10 7RH, United Kingdom

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