“Hello, Earth! Can you hear me?” That's voice more than 400,000 people received recently. It was from Philae, a space vehicle that landed on a comet(彗星)in 2014. However, its transmissions (传输信号)back home went silent since then.

It took a long time for Philae to make its way across the solar system (太阳系)and reach comet 67P/C-G. The pace vehicle got there aboard the Rosetta probe (探测器), which has been circling around the comet since Philae separated from it in November, 2014．

Philae's job was to collect materials to study the comet's composition. And for about two and a half days after landing, it did just that, sending the information back to scientists on Earth. But Philae's landing on the comet's icy surface had not been smooth. While touching down, it jumped up and ended up in the shadow of something like a huge rock. Philae runs on solar power, but there was no light in the place where it landed. In the end, it failed to work.

However，as comet 67P/C-G moved closer to the sun, more sunlight reached the space vehicle, allowing it to power up and come back online. Philae then sent something to Rosetta, which passed on the information back to Earth.

“We only received the information for about 85 seconds, but that's enough to let us know it is alive and well,”says Stephan Ulamec, who works for the European Space Agency.“We hope to work out where it landed exactly on the 4-kilometer-wide comet. Now we plan to change how Rosetta moves so that Philae can keep on communicating and receiving instructions.”

    Researchers found that walking around with a forced smile and fake happiness simply leads to people feeling unhappier. So, putting a brave face on your sadness could be harmful. The research also found that women suffered more than men when pretending to be happy.

    Dr. Brent Scott, who led the study, said employers should take note because forcing workers to smile when dealing with the public can result in bad outcomes. He said, “Smiling for the sake of smiling can lead to emotional tiredness, and that's bad for the organization.” He also said the research showed customer-service workers who had “fake smiles” throughout the day didn't want to work, so their productivity dropped.

    The study is one of the first of its kind to examine emotional expressions over a period of time and compare the different effects on men and women. Dr. Scott's team examined the effects of “surface acting”, or fake smiling, compared to “deep acting”, or making people smile by thinking of pleasant memories.

    Dr. Scott said, “Women were harmed more by surface acting, meaning their moods worsened even more than men's. However, they were helped more by deep acting, which means their moods improved more by thinking of pleasant memories.”

    According to Dr. Scott women tend to suffer more when pretending to be happy because they are expected to be more emotionally expressive than men. Therefore, forcing a smile while feeling down is more likely to go against their normal behavior and cause more harmful feelings.

    Although deep acting can improve moods a little in the short term, Dr. Scott says it's not a long-term solution to feeling unhappy. There have been some suggestions that if you do this over a long period you start to feel unreal. You're trying to develop positive emotions, but at the end of the day you may not feel like yourself any more.

    Angad Rekhi, a graduate student and an assistant professor of electrical engineering, has developed a wake-up receiver. This wake-up receiver has many potential applications, particularly in designing the next generation of net worked devices, including so called "smart" devices that can communicate directly with one another without human intervention (介入).

    Once attached to a device, a wake-up receiver listens for a unique ultrasonic（超声波）pattern that tells it when to turn the device on. It needs only a very small amount of power to maintain this constant listening, so it still saves energy overall while extending the battery life of the larger device. A well-designed wake-up receiver also allows the device to be turned on from a significant distance.

    Given the increased interest in networked devices, researchers and industry organizations are starting to define what features and techniques will become standard. Regardless of whether this ultrasound wake-up receiver is among these standard designs, it is likely wake-up receivers of some kind will be combined into commercial applications soon.

    By comparison, the ultrasound wake-up receiver requires a battery but has much greater range than the wirelessly powered devices, while still maintaining a long lifetime due to extremely low power draw. These two technologies-wireless power and wake-up receivers-would likely serve different purposes but both indicate at a turning point in devices that make up the Internet of Things.

    "In light of a long-promised future where interconnected, autonomous, widespread and unremarkable technologies make life easier, the networked devices available now, like video doorbells and app-enabled lights, seem like rather slight advances." the researchers said. They believe technologies like theirs could help cross the gap between the Internet of Things as we know it and the Internet of Things at its best-whatever that may be.

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.

    Years ago, I volunteered at a homeless shelter in Los Angeles, handing out food. Once I got talking with Albert, a tall and skinny young guy in line. He said he liked my socks. "Want to see mine?" he joked, lifting his leg. He was barefoot. I felt a sinking feeling in my stomach.

    The next day, after work, I stopped at Ross and filled up my truck with socks. The following early morning, I drove over to Santa Monica's Palisades Park, which is a common destination for homeless people.

    I took one of the bags from my trunk. It was still dark out. I headed for a group of three men, standing around a tree, probably using it as a windbreaker. Two were asleep under heavy blankets, and the third was digging through his collection. As I walked toward him, he watched me, perhaps questioning my motives. "I thought you guys might need some fresh new socks," I said, handing him a pair. He looked confused at first but took them and said, "Thank you." I gave him two more pairs for his friends.

    I moved on. An hour later, I had given out all the socks. Most people were sleeping, and I felt like Santa. I knew that when they wake up they would find a very meaningful present.

    That was nine years ago. Every week I'll hand out as many socks as I can. If I'm on vacation or on a business trip for more than a week, I bring a bag of socks with me and hand them out to the homeless on the streets in other states and countries.

    It's extremely satisfying to operate "under the radar(雷达)" to help make some people's lives a little bit easier. Part of me hopes to see Albert out there one of these days, but even if I don't, I like to think one of the pairs will find him.

Some people today might be early risers because of DNA they take after Neanderthals tens of thousands of years ago, suggests new research.

When early humans migrated from Africa to Eurasia roughly 70,000 years ago, some of them mated with Neanderthals, who had already adapted to the colder, darker climates of the north. The ripple (涟漪) effects of that intermating still exist today: Modern humans of non- African ancestry (血统) have between 1 and 4 percent Neanderthal DNA. Some of that DNA relates to sleep more specifically, the internal body clock known as the circadian rhythm.

For the new study, researchers compared DNA from today's humans and DNA from Neanderthal fossils (化石). In both groups, they found some of the same genetic variants involved with the circadian rhythm. And they found that modern humans who carry these variants also reported being early risers.

For Neanderthals, being "morning people" might not have been the real benefit of carrying these genes. Instead, scientists suggest, Neanderthals' DNA gave them faster, more flexible internal body clocks, which allowed them to adjust more easily to annual changes in daylight. This connection makes sense in the context of human history. When early humans moved north out of Africa, they would have experienced variable daylight hours--shorter days in the winter and longer days in the summer-for the first time. The Neanderthals' circadian rhythm genes likely helped early humans' offspring (后代) adapt to this new environment.

Notably, the findings do not prove that Neanderthal genes are responsible for the sleep habits of all early risers. Lots of different factors beyond genetics can contribute, including social and environmental influences. The study also only included DNA from a database called the U.K. Biobank-so the findings may not necessarily apply to all modern humans. Next, the research team hopes to study other genetic databases to see if the same link holds true for people of other ancestries. If the findings do apply more broadly, they may one day be useful for improving sleep in the modern world, where circadian rhythms are disturbed by night shifts and glowing smartphones.