【推荐2】Around and around they go — dogs are often seen chasing (追逐) their tails. There are several possible reasons for this behavior, as well as ways to thwart it.

Puppies and younger dogs may simply chase their own tails for fun. Puppies, especially, may not yet realize their tails are actually part of their own bodies.

Boredom may be another reason, especially when dogs are left alone for a long time. “Anytime a dog is not enriched or exercised fully, they have the potential to be bored,” Russell Hartstein, a dog behavioral consultant said. For these dogs, a simple solution may be to play fetch or take a walk. Most dogs would rather chase a ball than their own tails.

Another reason dogs may chase their tails is to seek attention. A dog’s owner may have rewarded this behavior by laughing or praising it. Even blaming a dog for tail chasing may draw attention that enhances this behavior. To control tail chasing, ignore the behavior while otherwise supplying the dog with a healthy amount of attention.

Unluckily, a number of physical diseases are linked with tail chasing. An injury to the tail, itching; or reaction to some food may cause dogs to bite or chase their tails. If dogs suddenly start chasing or biting their tails, the owners should schedule a visit with their vet.

“Interestingly, we found that dogs that received dietary supplements (补充剂), especially vitamins and minerals, expressed less tail chasing compared to dogs that did not receive any supplements,” Hartstein said. “In addition, compared with dogs that didn’t chase their tails, tail chasers were often shyer and had separated earlier from their mothers.”

If a dog is otherwise healthy, “practicing dog training and engaging their mental and emotional aspects of their lives will help stop tail chasing,” Hartstein said. “There’s no harm in training more with your dog and making sure they are fulfilled and enriched in every way possible.”

【推荐3】Most polar bears follow the sea ice as it grows and melts (融化) throughout the year. They depend on sea ice as the platform from which they hunt for sea animals. But as global temperatures have been rising, sea ice has been disappearing. And some bears have traveled so far in search of ice that they risk dying of hunger.

But in southeast Greenland, where the sea freezes over for just a few months, some polar bears are subsisting locally. Polar bears here have adapted to hunting from the glacial mélange, which is a mix of ice, snow and slush (雪泥). “These polar bears are residents of sea ice-free areas for more than eight months of the year,” says the biologist Kristin Laidre. “Normally, a polar bear wouldn’t be able to live without sea ice for that long.”

In northeast Greenland, the distance traveled by bears was 40 kilometers every four days. But in the southeast, the distance traveled was just one-fourth of the distance.“Apparently, those southeast Greenland bears are able to use resources that are present, so that they don’t have to make these big movements,”says Steven Amstrup, a zoologist. They make the sea ice home for a few months each winter and spring. For the rest of the year, the bears hunt from the glacial mélange. They use it just like sea ice.

However, researchers say that most polar bears will die out by 2100 unless emissions (排放) of climate-warming greenhouse gases are sharply cut back. Southeast Greenland and similar, small regions could become the last places for some of the remaining polar bears. Yet even they will disappear if climate change continues to melt the sea ice on which this species depends.

“Despite having learned to adapt to their slushy world, southeast Greenland polar bears will die without human climate action,” Amstrup says. “The glacial mélange isn’t widespread in the regions around the North Pole. And it could disappear if temperatures rise much more. Polar bears still suffer hunger.”

【推荐2】Some Chinese students born in the 1990’s created a microsatellite that took a stunning picture of the moon and the Earth in space, an image praised as one of the best of the two celestial bodies and one that Science magazine also used on Feb.15, 2019.

The photograph was done by the camera on Longjiang 2, a microsatellite developed by students at the Harbin Institute of Technology in Northeast China's Heilongjiang province.

Before its publication in the leading scientific journal, the picture had been widely circulated on mainstream media worldwide, with some foreign media outlets even praising it as one of the best photos of the moon and the earth so far.

Wei Mingchuan, born in 1991, was the chief designer responsible for the sub-system of Longjiang 2, a microsatellite launched last year together with Queqiao, the relay satellite for the Chang'e 4 lunar probe. Wei successfully developed LilacSat 1 -- the country's first microsatellite independently designed, developed and controlled by students -- and has been dubbed China's "youngest chief designer", despite being the oldest in his team.

Tai Mier, one of Wei's team members who was born in 1996, designed the camera on Longjiang 2 that captured the amazing picture of the moon and the Earth. Tai was only 20 years old when work on the project began.

The youngest member in the team is 20-year-old Huang Jiahe, who handled software design for the Longjiang 2 ground station. Beginning in primary school, Huang would buy all kinds of electronic components and parts. At first, he just simply disassembled and assembled the parts, but now he can design and create things. This young man, considered a genius by some, said that he is just curious and passionate about aerospace technology.

In their dormitory, aerospace-related items are everywhere. A postcard on the wall is printed with the words "we were born for our dreams", a reminder that the future has just begun for this youngest team of the Chang'e 4 mission.

【推荐3】He’s considered the father of the technological innovation, and apart from that, he was also known as a design perfectionist. There is no single executive or creator in the technology industry who is more creative and inspirational than him, and with that being said he was a one-in-billion creator.

On February 24, 1955, in San Francisco, California, United States, a baby named Steve Jobs entered the world. His parents’ inability to provide for him led to a difficult childhood, one in which he battled with his sense of self and felt constantly confused and unfulfilled. Nonetheless, who could have predicted that this person would cause such a dramatic shift in the information technology? The way Steve Jobs showed the world the new products and devices he was working on was truly out of this world, and that’s a big part of why he’s so beloved.

Steve Jobs was well-informed, but he was not a scholar. He possessed a high IQ but showed little enthusiasm for formal education. His main hobbies were playing tricks on people via phone and computer, goofing off with his best friends, and coming up with ground-breaking business concepts.

Steve Jobs’ philosophy on education is well-known at this point; he has stated publicly that he was only able to learn after leaving college. When Steve Jobs and his friend Wozniak were in their early 20s, they came up with the idea for the Apple Computer. Steve Jobs’ Volkswagen bus and Wozniak’s beloved scientific calculator were sold to finance the pair’s garage-based startup. Jobs and Wozniak have been given much of credit for democratizing the computer industry by making computers more user-friendly, portable, and affordable.

Wozniak envisioned a line of accessible and lightning-fast personal computers, and Jobs was put in charge of the company’s marketing and management. From the get-go, Apple sold the computers for up to $666. The unexpected greatness of their early success inspired them to develop more powerful machines. In the 70s, they accomplished what would become the company’s crowning achievement. Assembled by Apple, Inc. , the high-performance computer was an instant success in their home state of California, and its sales helped make Jobs a multimillionaire.

【推荐1】Network-based technologies have become increasingly widespread, and they are now being used by countless individuals, professionals, and businesses worldwide. Despite their advantages, most network-based systems are highly at risk of malicious (恶意的) attacks.

The consequences of a malicious attack on network-based systems can be extremely harmful. For instance, an attack on a power plant network could leave millions of individuals and offices without electricity, while attacks on social media networks can lead to exposure of user information.

To overcome the weaknesses of network-based systems, computer scientists worldwide have been trying to develop advanced intrusion detection systems (IDSs) (入侵检测系统) that could help to identify malicious attacks, increasing a network’s safety. In recent years, machine learning (ML) algorithms (机器学习算法) have been found to be particularly promising for automatically detecting attacks and intrusions on a network’s functioning.

An important step in the development and training of ML-based IDSs is the selection of data features that a model can rely or focus on when making predictions. Ideally, by analyzing large datasets, researchers should be able to identify the most suitable features for solving a given task using ML tools, and this can also be applied to intrusion detection.

Researchers at Canadian University Dubai in the UAE have recently developed a new feature selection method that could enable the development of more effective ML-based IDSs. This method was found to perform remarkably well when compared with other commonly employed feature selection techniques. Using the features they identified as most important for intrusion detection, the researchers created a highly efficient ML-based detection system. This system was found to be capable of distinguishing between DDoS attacks and harmless network signals with 99% accuracy.

In the future, the feature selection method developed by the researchers and their findings could help the development of new, highly effective IDSs. In addition, the system they created using the features they identified could be applied in real-world settings to detect malicious attacks on real networks.

【推荐2】For nearly every step of his almost 12-mile walk, Darryl Dyer has company. Flocks of crows follow him, signaling each other, because they all know that he’s the guy with the peanuts.

“They know your body type. The way you walk,” Dyer said. “They’ll take their young down and say: ‘You want to get to know this guy. He’s got the food.”

Scientists for years have known that crows have great memories, that they can recognize a human face and behavior, and can pass that information onto their babies.

Nowadays, researchers are trying to understand more about the crow’s brain and behavior, specifically what it does when the birds see one of their own die. They react loudly to the dead, but the reasons aren’t entirely known. Among the guesses is that they are mourning; losing a partner could be a significant moment for the social animals. Crows place sticks and other objects on dead birds—a funeral of sorts.

“Crows have evolved to have these complex social relationships, and they have a big brain,” said Kaeli Swift, who led the study.

How big of a brain? Crows are on par with smart mammals, like dolphins and monkeys, in brain-to-body proportion (比例). They have been known to be problem solvers and are among the few animals recorded to use tools.

In another part of the experiment, using slightly radioactive tracers, researchers measured the brain activity of crows after they were shown a dead bird. The scans showed the section of the hippocampus-the part involved in memory formation-light up at the sight of death. “In that particular situation at least, that crow was learning about a place, or a face, or a situation and associated it with that dead crow,” said Johin Marzluff, the lead researcher.