The top ten advances in Chinese science in 2019 were announced by the High Technology Research and Development Center (Basic Research Management Center) of the Ministry of Science and Technology on February 27, 2020.China’s Top 10 Scientific Advances in 2019 includes:
1.Preliminary evidence of lunar mantle material detection
Both the lunar crust and the mantle were formed during the early stages of the evolution of the moon. The energy generated by the collisional accretion process created a molten magma ocean. Heavier iron-magnesia minerals such as low-calcite, crystallize to form the mantle. However, no direct evidence related to the exact composition of the lunar mantle has been found in lunar samples returned from the Apollo and Luna missions, and inferences about the composition of the lunar mantle have not yet been well confirmed. A very large impact crater may penetrate the lunar crust, causing the mantle material to be excavated and may be detected and sampled. The Antarctic-Aitken Basin (SPA), located on the back of the moon, is about 2,500 kilometers in diameter. It is the oldest and largest impact structure on the moon’s surface and is most likely to penetrate the moon’s crust. However, remote sensing data obtained from existing lunar orbiters indicate that although the iron-magnesium mineral content in the SPA area is high, there is no evidence of widespread exposure of olivine. It is still controversial whether these materials may originate from the mantle.
China’s Chang’e-4 probe successfully landed in the von Carmen crater on the back of the moon in the SPA area, and carried out patrol detection using the lunar vehicle-Yutu-2. Li Chunlai’s research group and collaborators of the National Astronomical Observatory of the Chinese Academy of Sciences reported the preliminary spectral detection results of the visible light and near-infrared spectrometer (VNIS) configured on Yutu 2 and analyzed the existence of low-calcium (orthorhombic) pyroxene and olivine. This mineral combination is likely to represent deep matter originating from the mantle. Further analysis of the geological background indicates that these materials were excavated from the nearby Finsen impact crater with a diameter of 72 kilometers and ejected to the lunar mantle material at the Chang’e 4 landing site. The significance of this work is to reveal the material composition of the lunar mantle, provide new constraints for the study of the early magma ocean, and deepen the understanding of the formation and evolution of the lunar interior. “Yutu 2” will continue to explore these materials at the bottom of the von Carmen crater to understand their geological background, origin and composition, and provide a basis for future moon sample sampling and return missions.
2.Structure a heterogeneous chip for artificial general intelligence
There are generally two methods for the development of artificial general intelligence (AGI): computer science-oriented or neuroscience-oriented. The combination of the two is currently recognized as the best way to develop AGI. Because their concepts and coding schemes are fundamentally different, these two methods rely on completely different and incompatible computing platforms. It is very difficult to build an integrated computing platform, which hinders the development of AGI. Therefore, it is important to develop a universal platform that can support both popular computer science-based artificial neural networks and neuroscience-inspired models and algorithms.
Tsinghua University’s Shi Luping research team and collaborators have proposed a natural chip architecture that efficiently integrates the above two methods and provides a heterogeneous integrated collaborative computing platform. The chip uses a hybrid coding scheme with multi-core structure, reconfigurable components and streamlined data streams, which can simultaneously independently support computer science-based machine learning algorithms and neuroscience-led algorithms, as well as multiple coding schemes in neuroscience. Heterogeneous hybrid modeling provides new solutions. Using just one chip, the researchers demonstrated the synchronization of common algorithms and models in the unmanned bicycle system, real-time target detection, tracking, voice control, obstacle avoidance, obstacle avoidance, and balance control. The research is expected to pave the way for the development of more general-purpose hardware platforms and advance the development of AGI.
3.Propose treatment scheme for autoimmune diseases based on DNA detection enzyme regulation
There are thousands of types of viruses, and their infection characteristics and pathogenic methods are also ever-changing, but what’s changing is that when the virus invades, its own genetic material will inevitably be brought into the host cells. The body responds quickly to these foreign genetic materials (such as DNA), even at the cost of hurting itself, which is the main cause of lethal inflammation caused by viral infection. The knowledge about the immune response induced by foreign DNA goes back hundreds of years, but the mechanism behind it is unclear. In 2013, an important breakthrough was achieved internationally in this field. Scientists identified the protein cGAS (cycloguanylate-adenylate synthetase) as an intracellular DNA virus receptor. As cGAS was revealed, scientists discovered that in addition to detecting viral invasion, abnormal activation of cGAS also directly caused a class of autoimmune diseases. Therefore, finding effective ways to control cGAS activity and exploring its regulatory mechanism are of vital importance in the treatment of viral infections and autoimmune diseases.
Zhang Xuemin and Li Tao’s research group and collaborators of the Military Medical Research Institute (National Center for Biomedical Analysis) found that acetylation modification is a key molecular event that controls cGAS activity, and revealed the regulation behind it. The researchers identified three key acetylation sites of cGAS (K384, K394, and K414) and found that acetylation of any of these sites can cause cGAS to lose its activity. Furthermore, the researchers found that acetylsalicylic acid (aspirin) can force cGAS to undergo acetylation at the above-mentioned key sites, thereby inhibiting its activity. In addition, further investigation of cGAS regulation mechanism found that cGAS exists and functions as a complex in the cell. Using protein mass spectrometry, the researchers identified a key regulator of cGAS, G3BP1. Mechanism studies have revealed that G3BP1 binds to cGAS and helps cGAS to form polymers to ensure it can more efficiently recognize DNA. In the absence of G3BP1, cGAS activity was significantly reduced in cells. Importantly, the main component of green tea tea polyphenols, the natural small molecule compound EGCG, is an inhibitor of G3BP1. Researchers have found that EGCG can inhibit cGAS activation by interfering with the interaction between G3BP1 and cGAS. The above research not only reveals the key regulatory mechanisms of the body’s resistance to viral infections, but also finds effective cGAS inhibitors, providing a potential treatment strategy for autoimmune diseases such as AGS (Icardi syndrome).
4.Deciphering protein structure and function of algae underwater photosynthesis
The research team of Shen Jianren and Kuang Tingyun from the Institute of Botany, Chinese Academy of Sciences reported the high-resolution crystal structure of marine diatoms-Phaeodactylum tricornutum FCP, revealing 7 chlorophyll a, 2 chlorophyll c, and 7 fucoxanthin in the protein scaffold. The detailed binding site of phytoxin and possibly a fucoxanthin, thus revealing an efficient energy transfer pathway between chlorophyll a and c. The structure also shows the close interaction between fucoxanthin and chlorophyll, enabling energy to be efficiently transferred and quenched through fucoxanthin. The research team further collaborated with Sui Senfang’s research group at the School of Life Sciences of Tsinghua University to analyze the cryo-EM structure of the diatom photosystem II (PSII) and FCPII supercomplex with a resolution of 3.0 angstroms. The supercomplex consists of two PSII-FCPII monomers, each of which contains a PSII core complex with 24 subunits and 11 peripheral FCPII antenna subunits, of which the FCPII antenna consists of two FCPII four The polymer and three FCPII monomers are present. The entire PSII-FCPII dimer contains 230 chlorophyll a molecules, 58 chlorophyll c molecules, 146 carotenoid molecules, and manganese cluster complexes, electron transporters and a large number of lipid molecules. This structure reveals the characteristics of unique subunits in the core of diatom PSII and the arrangement of antenna subunits that are significantly different from those of higher plants PSII-LHCII complexes, as well as the huge pigment distribution network of diatoms. Light capture, energy transfer, and dissipation mechanisms provide a solid structural foundation.
5.High-temperature bulk metallic glass based on material genetic engineering
Metal glass has a unique disordered atomic structure, which makes it possess excellent mechanical and physical-chemical properties. It has been widely used in high-tech fields such as energy, communications, aerospace, and national defense, and is an important part of modern alloy materials. Due to the plastic flow of metallic glass near the glass transition temperature, the mechanical strength is significantly reduced, which severely limits their high temperature applications. Although metallic glass with a glass transition temperature greater than 1000 K has been developed, due to its narrow supercooled liquid phase region (the temperature range between the glass transition temperature and the crystallization temperature), its glass-forming ability is insufficient and difficult to form. Large-size materials; and its poor thermoforming performance makes it difficult to process parts. The key to the above-mentioned challenges lies in the rational design of the forming components of metallic glass. The metallic glasses with specific properties discovered so far are mainly the result of repeated experiments and attempts.
Liu Yanhui’s research group of the Institute of Physics, Chinese Academy of Sciences and collaborators developed a high-throughput experimental method based on the concept of material genetic engineering with high efficiency, non-destructiveness, and easy promotion. An Ir-Ni-Ta- (B) alloy was designed. In the system, high-temperature bulk metallic glass was obtained, and its glass transition temperature was as high as 1162 K. The newly developed metallic glass has extremely high strength at high temperatures, and the strength at 1000 K is as high as 3.7 gigapascals, far exceeding the previously reported bulk metallic glass and traditional high temperature alloys. The metallic glass has a subcooled liquid phase region of 136 K, which is wider than most of the previously reported metallic glasses, and its forming capacity can reach 3 mm, making it possible to obtain small-scale applications in high temperature or harsh environments through thermoplastic forming. component. The high-throughput experimental method developed by this research has strong practicability, overturning the “stir-fried” material development model in the metal glass field for 60 years, and confirmed the effectiveness and high efficiency of material genetic engineering in the development of new materials. Solving the problem of efficient exploration of new metallic glass materials has opened up new approaches, and also provided new ideas for the design of new high-temperature, high-performance alloy materials.
6.Elucidate the mechanism of thallium ions on improving the life of perovskite solar cells
Perovskite solar cells are a new generation of photovoltaic technology that has attracted much attention, and its working stability is the main obstacle to current industrialization. Traditional research mainly uses component optimization, packaging, interface modification, and ultraviolet light filtering to effectively suppress performance degradation caused by factors such as oxygen, moisture, and ultraviolet light, thereby improving device stability. However, to further improve the life of the device, it is necessary to develop a long-term effective method to suppress the intrinsic defects of the material during the service process.
In order to improve the intrinsic stability, Zhou Huanping’s research group of the School of Engineering of Peking University, Yan Chunhua / Sun Lingdong’s research group of the School of Chemistry and Molecular Engineering and their collaborators proposed that by introducing thorium ion pairs (Eu3 + / Eu2 +) into the perovskite active layer As a “redox shuttle”, Pb0 and I0 defects can be eliminated at the same time, and the service life of the device can be greatly improved. Interestingly, the ion pair was not significantly consumed during the use of the device, and the corresponding device’s efficiency reached a maximum of 21.52% (certified value is 20.52%), and there was no obvious hysteresis. At the same time, thin-film devices incorporating erbium ion pairs exhibit excellent thermal and light stability. After continuous sunlight or heating at 85 ° C for 1000 hours, the devices can still maintain the original efficiency of 91% and 89%, respectively; The point keeps 91% of its original efficiency after 500 hours of continuous work. This method solves an important essential factor that restricts the stability of lead-perovskite solar cells, and can be extended to other perovskite photovoltaic devices. It also has reference significance to other inorganic semiconductor devices facing similar problems.
7.Denisova found on the Tibetan Plateau
The Denisovans are a mysterious ancient human who has disappeared. Their understanding of the past is mainly based on the small amount of fossil fragments unearthed only in the Denisovan cave in Siberia and the high-quality paleogenetic information stored therein. Genetic studies have shown that Denisovans have genetic contributions to some modern low-altitude East Asian populations and high-altitude modern Tibetan populations, and are of great significance for the high-altitude environment adaptation of modern Tibetan populations. The lack of fossil morphological information makes it difficult for scientists to assess the links between Denisovans and the rich ancient human fossils scattered throughout Asia and elsewhere, and to accurately understand the relationship between Denisovans and modern Asian populations . In addition, the high-altitude environment-specific gene sources peculiar to modern Tibetans and other people on the Qinghai-Tibet Plateau, especially whether they inherited from the Denisovans, are very important and urgent scientific issues to be resolved.
Chen Fahu’s research group of the Qinghai-Tibet Plateau Research Institute of the Chinese Academy of Sciences, Zhang Dongju’s research group of Lanzhou University, and the Jean-Jacques Hublin research group of the Institute of Evolutionary Anthropology of the Max Planck Society of Germany, and other collaborators, have reported the identification of a Danisova by ancient protein analysis Mandible from the Baishiya cave in Xiahe County, Gansu Province, China. Researchers have determined that the mandible has a history of at least 160,000 years by uranium dating the carbonate nodules attached to the fossils. The fossil specimen is the first Denisova fossil evidence found outside the Denisova cave. A comprehensive analysis of the specimen also provides a wealth of physical morphological information for Denisova research, including jaw and tooth morphology. information. The study showed that before the arrival of modern Homo sapiens, the Denisovans had already lived in the high altitude areas of the Qinghai-Tibet Plateau in the late Middle Pleistocene, and successfully adapted to the high-altitude hypoxia environment.
8.Satellite test of gravitational-induced quantum decoherence model
Quantum mechanics and general relativity are the two pillars of modern physics. However, any theoretical work that attempts to fuse quantum mechanics with general relativity has encountered great difficulties. At present, there are many discussions on how to integrate quantum mechanics and gravity theory, but they generally lack experimental verification.
University of Science and Technology of China Pan Jianwei and colleagues Peng Chengzhi, Fan Jingyun and their collaborators, using the “Muzi” quantum scientific experimental satellite, are the first in the world to conduct an experimental test of gravity-induced quantum entanglement decoherence in space. Decoherence of quantum entangled photons in the gravitational field was tested. According to the “event form” theoretical model prediction, the propagation of entangled photon pairs in the gravitational field of the earth will be lost probabilistically; according to the existing quantum mechanical theory, all entangled photon pairs will maintain entangled properties. In the end, the satellite experimental test results did not support the prediction of the “event form” theoretical model, but were consistent with standard quantum theory. This is the first time in the world that a quantum satellite is used to experimentally test a theory that attempts to fuse quantum mechanics with general relativity in the gravitational field of the earth, which will greatly promote related basic theoretical and experimental research in physics.
9.Revealing the structure of African swine fever virus and its assembly mechanism
African swine fever virus (ASFV) is a huge and complex DNA virus that can cause domestic pigs and wild boars to suffer from acute, febrile and highly infectious diseases. The morbidity and mortality can reach up to 100%. Economic loss, no vaccine is currently available.
The team of Rao Zi and Wang Xiangxi from the Institute of Biophysics of the Chinese Academy of Sciences and the Buzhigao team from the Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, together with the Shanghai University of Science and Technology, have continuously collected high-quality data at the Cryo-EM Center of the Shanghai University of Science and Technology. The three-dimensional structure of the capsid of African swine fever virus was analyzed, and its resolution reached 4.1 angstroms. The capsid granules are large and complex, consisting of 17,280 protein subunits, including one major (p72) and four secondary capsid proteins (M1249L, p17, p49, and H240R), which are assembled into a five-fold symmetry The composite structure of the body and the triple symmetric body. The major capsid protein p72 atomic resolution structure shows a potential conformational epitope of African swine fever virus, which is significantly different from other nuclear cytoplasmic large DNA viruses (NCLDVs). The secondary capsid protein forms a complex protein interaction network on the inner surface of the capsid, which mediates the assembly of the capsid and stabilizes the structure of the capsid by regulating the forces between adjacent viral shell microbodies. As the core organizer, the 100-nm-long M1249L protein bridges two adjacent pentads along each edge of the triplet, forming an extended intermolecular network with other capsid proteins, driving the capsid. Formation of the frame. These structural details reveal the molecular basis of capsid stability and assembly, and have important theoretical guiding significance for the development of African swine fever vaccine.
10.First observation of 3D quantum Hall effect
The discovery of the quantum Hall effect in a two-dimensional electronic system makes topology play a central role in condensed matter physics. More than 30 years ago, Bertrand Halperin et al. Theoretically predicted that the quantum Hall effect may be generated in a three-dimensional electron gas system, but so far, no “three-dimensional quantum Hall effect” has been observed experimentally.
Zhang Liyuan’s research group of the Department of Physics, Southern University of Science and Technology, Qiao Zhenhua’s research group of the Department of Physics, University of Science and Technology of China, and Yang Shengyuan of Singapore University of Science and Technology have collaborated to realize the “three-dimensional quantum Hall effect” for the first time in bulk zirconium telluride (ZrTe5) crystals. “. The researchers performed low-temperature electron transport measurements on a single crystal of zirconium telluride body in a magnetic field, and reached an extreme quantum limit state (only the lowest Landau level is occupied) in a relatively low magnetic field. In this state, the researchers observed a near zero non-dissipative longitudinal resistance and formed a good Hall resistance platform proportional to half the Fermi wavelength along the magnetic field direction. These are the three-dimensional Hall effect Hard marks appeared. Theoretical analysis also shows that the effect results from the Fermi surface instability driven by the charge density wave generated by the enhanced electronic correlation under the extreme quantum limit. By further increasing the magnetic field strength, both the longitudinal resistance and the Hall resistance are greatly increased, showing a metal-insulator phase transition. This research advance provides experimental evidence for the three-dimensional quantum Hall effect and provides a promising platform for further exploration of singular quantum phases and their phase transitions in three-dimensional electronic systems.