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Robot

Can grab the "paper-cut" hand of raw egg yolk

The art of three-dimensional origami makes the two-dimensional sheet material form a three-dimensional structure by cutting and folding. However, it is still very difficult to reverse design the shape and cutting method of the two-dimensional sheet according to the required three-dimensional structure, especially the three-dimensional structure with complex curved surface. However, a recent study in the journal Nature Communications suggests a new way to solve this problem.

Scientists continuously cut a large number of parallel slits on two-dimensional slices and found that the boundary curvature of these slits largely determines the three-dimensional structure after folding. The final forming can be controlled by setting the boundary curvature of the target and adjusting the stretching force and direction during folding, which greatly simplifies the design process compared with setting the complex shear scheme directly. On the basis of this, the scientists proposed a method to reverse the two-dimensional precursors according to the boundary curvature of the three-dimensional structure, and designed a polymer sheet robot hand which can grasp objects such as raw egg yolk, live fish, hair and so on. and the knee joint hot application which can dynamically adapt to the surface deformation. This new method has great application potential in industry, such as designing programmable software robots.

Astronomy

Astronomers discover a new type of celestial bodies

The phenomenon of celestial bodies flickering and dimming in the universe is called "transient", which is characterized by the death of massive stars and their residues. For example, the slow transient of a supernova lights up the star in a few days and extinguishes after a few months, while the rapid transient of a pulsar often occurs in milliseconds to seconds. However, a study published on January 26th in the journal Nature found that the transient properties of celestial bodies are different from those of previous ones.

The researchers analyzed data from the Australian square kilometer array low-frequency pilot telescope (SKA) Merchison wide-field array (MWA) and located the source of radiation objects in the Milky way about 4000 light-years from Earth. During the hours of observation, the object emits extremely bright radio signals every 20 minutes. It is smaller than the sun and emits highly polarized radio waves, indicating that celestial bodies have a strong magnetic field. These characteristics are consistent with the ultra-long period magnetic gyrostar (magnetar), which is a kind of neutron star with slow rotation, which is only predicted theoretically. The study found that the brightness of the celestial bodies exceeded astronomers' expectations of ultra-long period magnetars. The researchers say the object can efficiently convert magnetic energy into radio waves. They plan to go back to the MWA dataset to find more similar objects.

Physics

Realizing the Schwinger effect in the laboratory

Scientists once thought that a vacuum was a completely empty space with no matter or elementary particles in it. However, Nobel laureate Julian Schwinger (Julian Schwinger) predicted 70 years ago that a strong electric or magnetic field could cause vacuum to spontaneously produce elementary particles, known as the "Schwinger effect". This phenomenon requires extremely strong electromagnetic fields and usually occurs only in cosmic events, such as around magnetars or in high-energy collisions between nuclei. Recently, however, in a study published in Science, researchers achieved a Schwinger-like effect in the laboratory by increasing the current of specially designed graphene equipment.

The researchers used graphene to make some specially designed superlattices and constraint structures to improve the strength of the electric field and to achieve an unusually strong electric field in the desktop space. Under the strong electric field, the researchers observed the spontaneous generation of electron-hole pairs, and the details of the generation process were in good agreement with the theoretical prediction. In addition, the researchers accelerated the generated electrons to 1max 300 at the speed of light and observed that the electrons became ultra-bright, providing a higher-than-theoretical current. The researchers' theoretical description of the process is very different from Schwinger's description of the vacuum.

Geoscience

Using the shells of marine animals to indicate the marine environment in ancient times.

At the end of the Permian period 250 million years ago, the most serious mass extinction event on earth-the Permian-Triassic extinction event occurred, resulting in about 90% of the extinction of organisms. Some studies have shown that the mass extinction was caused by violent volcanic eruptions and released large amounts of carbon dioxide into the atmosphere, so the theory is that Shanghai Ocean will absorb some of the carbon dioxide, leading to ocean acidification. However, previous studies based on chemical evidence of marine rocks have not been unified. In addition, scientists often explore the events of the earth hundreds of millions of years ago by analyzing marine rocks and fossils. Recently, a study published in the Science report for the first time analyzed the fossils of the shells of marine molluscs, suggesting that the ocean did not acidify at the end of the Permian.

The researchers collected fossils from the shells of conch and bivalve molluscs that lived at the end of the Permian at what is now Svalbard, Norway, and analyzed more than 2300 fossils under a microscope. The shells of these marine animals are made up of a calcium carbonate mineral, so they can be dissolved and damaged in an acidic environment. But they found that the fossils were in good shape and showed no signs of being damaged by acidic water such as holes, suggesting that the ocean may not have been acidified at the end of the Permian.

Health

A large number of adults are unable to accurately judge their body mass index and body shape.

A recent study published in the Science report shows that less than 2 percent of adults can correctly estimate their body mass index (BMI), and less than half of them can correctly judge their body size. The researchers surveyed 774 Polish adults with an average age of 36, of whom 60.7% were women. They calculated the adults' BMI from 2010 to 2011 and surveyed their satisfaction with their bodies, their BMI and their body size estimates.

The researchers found that 63.5% of people in the experiment could correctly estimate their body mass index and 49.5% could correctly estimate their body shape. They also found that these subjects tended to underestimate their BMI and body size. Among them, 17.6% of BMI healthy people thought their BMI was thin, 14.3% of BMI overweight people thought their BMI was healthy, and 41.6% of BMI obese people thought their BMI was overweight. In addition, men are significantly more likely than women to underestimate their BMI and body size, and are more likely to be satisfied with their body shape.

Physics

The field installation of Jiangmen neutrino experimental detector of the Chinese Academy of Sciences has been carried out in an all-round way.

According to the Institute of High Energy Physics of the Chinese Academy of Sciences, on January 21, the first support column of the main structure of the stainless steel reticulated shell of the Jiangmen neutrino experimental center was successfully hoisted and placed, which also marked the full start of the field installation of the Jiangmen neutrino experimental detector. The stainless steel reticulated shell is one of the largest single stainless steel main structures in China, with a diameter of 41 meters. it is made of about 900tons of low radioactive background stainless steel welded into components in the factory and transported to th