【推荐1】Why do cats purr(发出咕噜声)?

We’ve all heard cats meow, but why do most of them purr?     1     Some believe that they are simply happy. Some suggest that they may be in need of something.

    2     Cats do purr when they show their appreciation for attention. They also make the noise when not in our company. The purring noise is a continuous sound that occurs while they both breathe in and out.

When it comes to how cats purr, most people believe that the cat’s brain signals the muscles to vibrate(震动), which produces the noise.     3     Some argue that the cat intends to purr, while others say it may be due to chemicals released by the brain as a reaction to pleasure or pain.

According to Leslie A. Lyons, an assistant professor at the School of Veterinary Medicine at the University of California, cats often purr while stressed, for example, when they head to the vets or are recovering from an injury.

    4     Some scientists believe it may actually promote muscle development, heal bones and injuries, ease breathing and reduce pain.     5    

In a word, the purring of a cat may have more uses than just telling you they’re enjoying attention.

【推荐2】“They’re all in trouble,” says Kenyan ecologist Paula Kahumbu. “All elephants are in major, major trouble.”

Populations of the three species have reduced: savanna elephants, the largest land animals on the planet; forest elephants, their straight-tusked cousins; and the smaller-eared, Asian elephants, about a third of which live in fixed zone.

And we’re to blame. We’ve expanded (扩张) into elephant habitats, building homes and roads, cutting down forests and planting crops. More cruelly, people have a strong desire for ivory items that come from a dead elephant’s tusk. Although elephants are difficult to count, one study suggests that the African continent may have been home to some 26 million elephants at the beginning of the 19th century. That number has dropped sharply, becoming dangerously low in the past five decades, with the rise of poaching. Now there are as few as 415, 000 elephants in Africa. In Asia, there may likely be only 50, 000 in the wild.

Poaching doesn’t just destroy animals, says Kahumbu, CEO of the Kenyan conservation organization WildlifeDirect; it damages society. That’s why her organization monitored poaching cases in Kenyan courts, launched a campaign called Hands Off Our Elephants, and educates children on the value of wildlife. Kahumbu’s goal is great and urgent: to change “the whole national consciousness (意识) about conservation.”

Now, she’s taking her message to an international stage with Secrets of the Elephants, a four-part series on National Geographic and Disney. It explores the hidden lives of Elephants in four habitats — Asia, plus African forests, deserts, and savannas — as well as the people who are racing to save the animals.

【推荐1】The color blue is very rare in nature, with fewer than one in 10 plants sporting the common human favorite. To present this color, they have to perform tricks to make themselves blue to the human eyes. In some lowers like bluebells, it primarily occurs when naturally occurring pigments (色素) are mixed the way you can mix different paints to change the color.

For blueberries, the blue comes on the naturally produced thin layer of wax (蜡) on their skin, which often serves as a self-cleaning coating or for added protection in the plant kingdom. “The blue of most fruits is in their pigmented juices. That isn’t the case with blueberries,” says Rox Middleton, co-author of a study published in Science Advances.

In the study, Middleton and his team examined the wax of a blueberry using an electron microscope. They found that the layer of wax is composed of tiny structures that work by scattering (散射) blue and UV light from the sun, while absorbing most of other colors of light. The arrangement makes the berries appear blue to humans and blue-UV to birds and other species that can see UV light, despite not having blue pigments in the waxy skin itself.

To look closer, they removed the outer wax and reshaped it on a black card. They created a new blue-UV coating and removed a very thin substance that creates color called a colorant from the skin. “The colorants scatter blue and UV, letting the other colors pass through without absorption,” says Middleton. “That’s why it’s so important that there are dark pigments underneath to ‘mop up’ the rest of the light. If there was a bright pigment or white scattering material underneath, that light would come through, and the color would look mixed or washed out.”

The study does show that nature has developed a “really neat trick” in the form of a very thin layer for an important colorant. Reproducing this colorant in the lab could make a way for new methods of creating pigments.

【推荐3】If you hold up a seashell to your ear, you will hear the sea, no matter how far inland you currently are. In fact, it is not the case. So, what’s actually going on here?

One popular explanation is that you are listening to your own blood coursing through you. Popular as this blood theory is, it doesn’t hold water. “Press your ear to a shell and listen, then run around on the beach for a few minutes to increase the blood flow all through your body, and again listen to your magic shell,” Kruszelnicki wrote. “You’ll find that the loudness of the ‘sound of the sea is still the same’.”

If we truly were hearing the sound of our blood rushing through our bodies, that wouldn’t be the case: exercising makes your blood pressure rise, which would thus increase the supposed sounds being “reflected” by the shell. The fact that we don’t hear a difference before and after exercise, therefore, makes quite an evident statement.

There’s another idea that the “sea” you can hear in a shell is actually air-air flowing through the shell and out again, which creates the noise. “In a soundproof room, you won’t hear anything from a shell,” confirmed Andrew King, director of the University of Oxford’s Centre for Integrative Neuroscience. “Background noise must be present.” That’s the biggest clue as to what’s really going on here: the sounds we hear “inside” seashells are not coming from inside our bodies, but rather around them.

“You are hearing surrounding or background noise that has been increased in amplitude (振幅) by the physical characteristic of the seashell,” King explained, “the specific sounds we hear within a shell depend on the exact shape of itself-the hard, curved surfaces inside the shell cause the sound waves that enter to bounce around, increasing some frequencies while reducing others.”

Seashells may be the most poetic of ways to experience this resonance (共振), but they’re definitely not the only method - pretty much any convex (凹面的) surface will do.

【推荐2】Scientists have discovered a new way of administering oxygen to the blood which could allow people to stay alive without breathing. The procedure, which works by injecting oxygen molecules enclosed in fatty molecules directly into the bloodstream, could extend an extra 30 minutes of life when they cannot breathe.

John Kheir, a doctor of the Boston Children’s Hospital, was inspired to begin his groundbreaking research after he experienced a patient’s tragic death, according to Science Daily. He was operating on a young girl whose pneumonia led to deadly brain damage after doctors were unable to place her on a breathing machine in time to save her.

In response, Dr Kheir started working on the idea of inserting oxygen directly into the blood. Early experiments showed that the intervention could in theory be very successful, he said, “We drew each other’s blood, mixed it in a test. tube with the microparticles, and watched blue blood turn immediately red, right before our eyes.” However, injecting pure oxygen into the bloodstream in gas form failed miserably when it was attempted 100 years ago, as it formed dangerous bubbles in the veins.

Much of Dr Kheir’s research therefore involved finding a substance which could surround the oxygen and allow it to be suspended in a liquid for injection into the body. He found that using fatty molecules was the best way to keep oxygen after using sound waves to trap the two substances together into small particles that can only be seen with the help of a. microscope. The particles were then made up into a liquid which is very heavily oxygenated—carrying “three to four times the oxygen content of our own red blood cells”, according to Dr Kheir.

When used on humans, the oxygen could probably last for up to 30 minutes, though injecting it for any longer could damage the patient’s blood. “This is a short-term oxygen substitute—a way to safely inject oxygen gas to support patients during a critical few minutes,” Dr Kheir said. He added that he thought the technique could become routine for doctors dealing with emergency situations.

【推荐3】Sixty percent of Americans play video games daily, according to Techjury. In order to escape from the reality of quarantine (隔离), more people have turned to video games and VR (virtual reality) has become more popular than ever.

The world of VR isn't new to the gaming industry. It has been an ongoing concept for years, dating back to the 1800s. NASA popularized VR technology in 1989, bringing light to advancements that had never been seen before, and in 1991, SEGA introduced VR to gamers.

Gaming companies such as Oculus and HTC have redefined gaming by allowing players to involve themselves deeply in the world of VR through personal headsets. VR users are able to socialize through chat rooms, create 3D art and exercise through heart-pumping gameplay. Once a user puts on a headset, they are immediately transported into a virtual world. This allows the player to have a better experience compared to simply staring at a TV with a game controller.

Although VR has many positive aspects, using virtual reality too much can cause health problems among users. When using VR, it is common for people to lose spatial (空间的) awareness. Therefore, users are encouraged to play in an area that is clear of furniture and other objects causing potential danger. Eye strain can also be caused by using VR too much, so it is important to limit your time playing in virtual reality and take breaks in order to minimize the possibility of experiencing negative health effects.

How VR will develop in the future is unknown to us. However, new advancements for it are on the way. Teslasuit, a company specializing in VR equipment, is creating haptic (触觉的) suits for VR gameplay. These suits will allow users to feel aspects of VR while in game and will increase involvement, build 360-degree awareness and engage muscle memory. There are an endless number of possibilities that users                                               can experience and create in VR, and the boundaries of the virtual world are limitless.