Sometimes, you just can't help it. Maybe you're watching a sad movie, or thinking about the friend who moved away. Next thing you know, your eyes are watering, and you havetears running down your cheeks. Why do peoplecry when they are emotional? What are tears? Scientists are working hard to find the answers to these questions.

    Ad Vingerhoets is a professor of psychology at Tilburg University, in the Netherlands. He is one ofthe few scientists in the world who have studied crying. According to Vingerhoets, there are three types of tears. Basal tearsare the first type. Theylubricate(润滑) the eyes andact as a protective barrier between the eye and the rest of the World. Next arereflex tears. They wash youreyes clean when something gets in them. Finally, there are emotional tears. “These are released in response to emotional states, ”explains Vingerhoets. “Especially when we feel helpless.”

    Scientists believe that crying has something to do with how humans developed and learned to depend on each other.“Humans are very complex social creatures,”says Lauren Bylsma, a professor at the University of Pittsburgh, in Pennsylvania.“It seems that tears serve to arouse help and support from others," She says. “Another reason we weep is that humans have the longest developmental period of almost any animal. It takes along time to grow up. ”

    Vingerhoets agrees. “I think that the reason why humans shed tears(流眼泪) has somethingto do with our childhood,”he says. “That's the time when we are stir dependent on adults for love and protection and care. The major advantage of emotional tears is that you can target them at a specific person.”Vingerhoets says this ability to target someone could have come in hand in prehistorictimes, when humans were living among dangerous animals. Crying couldattract predators(捕食者). Tears were asafer way to get attention. In this case, it is better to use a silent signal to ask for help,”he says.

    Vingerhoets and Bylsma do frequent studies to better understand why humans cry. According to Byhma, there is still much more to discover. “It's surprising,”she says,“how much we still don't know.”

    Boston Tourist Attractions and Sightseeing

    Duck Tours

    One of the most popular tours in and around Boston are the legendary Duck Tours, which show you the best that the city has to offer. World War II vehicles take you on a scenic drive around the most famous sites and attractions in the city. With interesting explanation, this novel tour is an enjoyable and fun way to see the city and very much recommended.

    New England Aquarium

The aquarium is home to over 7,000 fish and a collection of many different sea creatures. The city's most visited tourist attraction is complete with exhibit space, gift shop and a cafe with spectacular views of the city and harbor. It also offers whale-watching tours with indoor and outdoor seating — and even seal or walrus (海象) shows.

    Boston Public Library

    Built in 1848, the Boston Public Library was the first free publicly supported city library in America. With more than 650,000 photographs, 100,000 prints and 250 different papers in the “Newspaper Room” the library now has Internet access, two restaurants and an on-line store with reproductions of its priceless artwork. All exhibits are open to the public and books m only the beginning.

    Bull and Finch Pub - Home of Cheers

    This world-famous pub is the inspiration for the hugely successful sitcom (情景喜剧) “Cheers”. Although the outside is the same as on television, the inside is completely different. However, although unexpected, this is not a real disappointment as the busy pub is full of reminders of Cheers. The menu serves typical bar food, and is very popular with tourists

    If visiting family or staying at one of the luxury Boston hotels downtown, you may want to corner purchasing a “Boston City Pass” as this will enable you to pay half price for most the finest attractions.

    Not all think laughter is the best medicine, but it seems to help. So scientists carried on a new study of diabetes (糖尿病) patients who were given a good dose of humor for a year to prove it.

    Researchers divided 20 high­risk diabetic patients into two groups. Both groups were given standard diabetes medicine. Group L viewed 30 minutes of humor of their choice, while Group C. the control group. did not. This went on for a year of treatments.

    By two months into the study. the patients in the laughter group had lower level of the hormones epinephrine (肾上腺素), considered to cause stress. which is known to be deadly. After the 12 months. HDL cholesterol rises 26 percent in Group L but only 3 percent in Group C. In another measure. C­reactive proteins, a maker of heart disease. drop 66 percent in the laughter group but only 26 percent in the control group.

    “The best doctors believe that there is a physical good brought about by the positive emotion, happy laughter. ”said study leader Lee Berk of Loma Linda University. And other research has found that humor makes us more hopeful. Still, more study is needed, Berk said. The research by Berk found that humor can bring about similar changes in body chemistry. which was proved in the new study. The research result will be presented this month at the meeting in the US. Research at the University of Maryland School of Medicine shows that laughter causes the inner lining of blood vessels to expand. increasing blood flow in a way thought to be healthy.

    “Lifestyle choices have an important effect on health and these are choices which we and patients should pay attention to. rather than prevention and treatment,”Berk said in a statement this week.

    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（虚拟购物车）. When you've done shopping, you can just leave the store. Shortly after, we'll charge your Amazon account and send you a receipt(收据).

    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 foodstuff 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(紧凑的), 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 smartphone, 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.

    Not sure what gift to get your loved ones? Think technology! You may even find something special for yourself!

    Mini Quadcopter

    Would you like to have a flying toy, but lack space to fly one? Consider a Mini Quadcopter that is small enough to fit inside your hand. This Mini Quadcopter can be controlled to fly in any direction with its remote control. The Mini Quadcopter is available from Hammacher Schlemmer for $39.95.

    Selfie Toaster

    Does your sweetie like taking selfies and eating toast? Well, why not combine the two with the Selfie Toaster? The Selfie Toaster crates an image on the piece of toast so you can smile at yourself every morning. The Selfie Toaster is available from Etsy for $10.95.

    Amazon Echo

    Give the knowledge of the world with the Amazon Echo.

    The advice can answer questions, tell you about weather conditions, tell jokes, play music and more. The Echo also acts as a Bluetooth speaker so you can connect your phone and listen to your favorite songs. The Echo is available from Amazon for $179.

    Indoor Snowfall Light

    Get into the spirit of the holiday season in your home with the Indoor Snowfall Light. The light shows snowflake shapes in your room to give you the feeling of a winter snowfall. You can control the speed of the snowfall, unlike the real whether. The Indoor Snowfall Light is available from Sharper Image for $59.99.

    Most people agree that eating healthy food is important. But sometimes making good food choices can be difficult. Now, there are apps that can help people learn about the food they eat to improve their health and their dining out experience.

    Open Table app

    Open Table app helps people choose restaurants when they want to go out to eat. It is a free service that shows users restaurant available based on where and when they want to dine. It gives users points when they make reservations(预定), which can add up to discounts on restaurant visits.

    Max McCalman's Cheese&Wine Pairing app

    Wine and cheese can be a great combination. But which wines go best with which cheeses? Max McCalman's Cheese&Wine Pairing app can help. It provides information about hundreds of different cheeses and suggests wines to pair with each. Max McCalman's Cheese&Wine Pairing app is free.

    HappyCow app

Vegetarians do not eat animal meat. Vegans do not eat any animal products. The HappyCow app is made for both groups. Users can search for vegetarian-vegan restaurants and stores around the world.

    LocalEats app

    Restaurant chains, like McDonalds, can be found almost anywhere a person might travel. But sometimes travelers want to eat like locals. The LocalEats app is designed for that. It can help you find local restaurants in major cities in the US and in other countries. It costs about a dollar.

    Where Chefs Eat app

    "Where Chefs Eat" is a 975-pagc book. Most people would not want to carry that around. But there is a much lighter app version of the same name for just $15. Six hundred chefs provide information on 3,000 restaurants around the world on the Where Chefs Eat app.