Discovery of the largest comet so far, about the size of Tianjin | Global scientific news

? Astronomy?

The largest known long-period comet

On January 8 this year, a team of researchers at the University of California, Los Angeles (UCLA) used the Hubble Space Telescope to identify comet Cmax 2014 UN??? Five pictures were taken. Combined with radio data from the Atacama large millimeter / submillimeter wave array (ALMA), the team confirmed that the effective diameter of the comet's nucleus is 119 ±15km, making it the largest known long-period comet. The results are published in the Astrophysical Journal KuaiBao. Tianjin has an area of 11966 square kilometers and an equivalent diameter of about 120km. The diameter of the comet is about the same as that of Tianjin.

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The comet was first observed in 2010. Its orbital eccentricity can reach 0.9993. The perihelion is 10.9 times the distance from the sun (1 astronomical unit is the average distance between the earth and the sun). Outside the orbit of Saturn, the aphelion is 15700 times the astronomical unit and is located in the Oort cloud. Now, it is about 20 times the distance from the sun and flies at a speed of about 35,000 kilometers per hour. The comet will reach perihelion around 2031.

? Chemistry?

How biomolecule mixtures form self-organizing structures

All organisms have the same basic components, such as the 20 amino acids used to make up proteins. Understanding how these basic components "communicate", "interact" and form self-organizing patterns is helpful for us to understand how organisms create functions. it also helps us to emulate the adaptive, growth and repair capabilities of biological tissues to develop new materials and technologies. Recently, a study published in Chem provides a new way to understand the adaptive function of biology.

Using a new synthesis method, the researchers systematically synthesized a mixture of dipeptide molecules (215 molecules) in a test tube, causing them to interact and react under the action of a catalyst. to simulate the spontaneous polymerization or decomposition of biomolecules as the surrounding environment changes, and use tracking techniques to observe these complex "interaction" patterns. They found that the interaction between dipeptide molecules is closely related to environmental conditions. This study starts from the simplest molecules and synthesizes complex biomolecules, which provides a new idea for explaining biological functions from a chemical point of view.

? Paleontology?

The largest early Triassic ichthyosaur fossil in China?

At present, ichthyosaurs first appeared in the early Triassic about 250 million years ago, and most of them were small individuals no more than 1.5m in length. Recently, Chinese scientists reported in PeerJ magazine an early Triassic ichthyosaur fossil from Shibao area, Longlin County, Baise City, Guangxi. This is the largest early Triassic ichthyosaur fossil found in China, with a total length of 3 meters, and belongs to a new genus and species in the world, which has been named Baisesaurus robustus.

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The fossil was found in a marine formation in 2017 and was initially confirmed to be a vertebrate. After restoration, scientists found that the fossil mainly contained the first half of the torso and had the typical characteristics of marine reptiles such as double concave vertebrae, but because the characteristics of key parts such as skulls and most appendage bones were not preserved, so identification is faced with some difficulties. After multiple comparative studies, scientists have finally identified some key features, including some unique features of ichthyosaurs, which are different from other marine reptiles such as fin dinosaurs. It is estimated that the total length of the individual to which the fossil belongs can reach 3 meters, and the recovered appearance is similar to that of modern dolphins. Scientists believe that the stout ichthyosaur may have a stronger ability to swim than other early ichthyosaurs, may have been able to travel longer ocean distances and migrate, and may have been advanced predators in the oceans at that time. (China Science Daily)

? Neuroscience?

Mastering two languages may delay brain aging

As people age, the gray matter and white matter of the brain will gradually shrink, and people often face neurodegenerative diseases and cognitive aging. The stronger and more complex the network between neurons in the brain, the better the cognitive ability is retained in old age, that is, the greater the cognitive stock (cognitive reserve). Previous studies have shown that factors such as the level of education can affect people's cognitive stock. Bilingual learning may help fight brain aging, according to a study published in the Frontier of Psychology.

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The researchers included 63 people over the age of 60 who were in good health, had no history of mental illness or neurodegenerative diseases, and knew at least one foreign language (with unlimited fluency). Participants are required to complete the assigned cognitive tasks to test their ability to identify targets under interference. The experimental results show that the subjects with longer foreign language learning years and more fluent foreign languages perform better in the test, and the influence of fluency is greater than that of learning years. This study and previous studies have shown that multilingual learning experience not only improves the executive function of the brain, but also helps to maintain memory and liquid intelligence (an ability that gradually decreases as the nervous system matures) and slows the progression of neurodegenerative diseases.

? Chemistry?

Using sunlight to "upgrade" plastic waste

Styrofoam egg boxes, rigid plastic optical disk boxes, drinking cups and most other common plastic products are made of polystyrene (PS). Plastic waste is usually treated by landfill, incineration and recycling, in which the existing recycling method is heat treatment, which often uses environmentally unfriendly fossil fuels. Recently, a study published in the Journal of the American Chemical Society uses visible light and oxygen to convert PS to benzoic acid in the presence of ferric trichloride catalyst.

The researchers selected PS materials such as white coffee cup lid, styrofoam and transparent lid and found that they were degraded by white light and catalyzed by ferric trichloride. Moreover, under the condition of sufficient oxygen, the high molecular weight PS can be degraded from more than 90kg/mol to less than 1kg/mol, and there is 23% benzoic acid in the degradation products (commonly used in perfumes, preservatives, etc.). Through experiments, they found that under the irradiation of white light, ferric trichloride will split and produce chlorine free radicals. Chlorine free radicals can capture the electron-rich hydrogen atoms from the polymer PS skeleton, thus promoting the degradation of PS. The researchers say the photochemical process can degrade plastics even if they are made of composite or insoluble materials.

? Healthy?

Antibiotics found in "antibiotic-free" beef

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The researchers collected and tested urine samples from 312 batches of nearly 700 cattle from 33 different USDA-certified antibiotic-free farms that were about to be slaughtered and sold. It was found that at least one cow tested positive in 42% of the farms. This shows that today's "antibiotic-free feeding" label lacks integrity. This is because the USDA approves suppliers to use these labels on the market, but does not enforce verification. The researchers suggest that agencies and retailers should strengthen verification and enforcement, and before that, consumers are advised not to blindly rely on the accuracy of these labels.

? COVID-19 epidemic situation?

As of 10:00 on April 13th, according to the latest statistics of Johns Hopkins University, there were 500,363,741 confirmed cases and 6,183,944 deaths of COVID-19 worldwide.

From 0 to 24:00 on April 12, 31 provinces (autonomous regions, munici