On February 27, 2020, the High Technology Research and Development Center (Basic Research Management Center) of the Ministry of Science and Technology released the top ten advances in Chinese science in 2019: detecting preliminary evidence of the exposure of lunar mantle materials, constructing an isomeric chip for artificial general intelligence, proposing an autoimmune disease treatment plan based on DNA detection enzyme regulation, cracking the protein structure and function of algal underwater photosynthesis, and developing high-temperature block metal glass based on material genetic engineering. 10 major scientific advances, including elucidating the mechanism of europium ions on increasing the life of perovskite solar cells, discovering Denisovans on the Qinghai-Tibet Plateau, realizing satellite testing of gravitationally induced quantum decoherence models, revealing the structure of African swine fever virus and its assembly mechanism, and observing the three-dimensional quantum Hall effect for the first time, were selected.
Introduction to the Top Ten Progresses of Chinese Science in 2019
01. Preliminary evidence of exposure of lunar mantle material was detected
Both the lunar crust and the lunar mantle were formed in the earliest stages of lunar evolution, and the energy generated by the impact hyperplasia process created a molten magma ocean, the lighter calcium-rich plagioclase components floated up to form the lunar crust, and the heavier iron-magnesium mineral crystals such as olivine and low-calcium pyroxene sank to form the lunar mantle. However, no direct evidence of the accurate material composition of the lunar mantle was found in lunar samples returned from the Apollo and Luna missions, and the inferences about the composition of the lunar mantle have not been well confirmed so far. Very large diameter craters have the potential to penetrate the lunar crust, allowing the lunar mantle material to be excavated and possibly detected and sampled. Located on the far side of the Moon, the South Pole-Aitken Basin (SPA), which is about 2,500 km in diameter, is the oldest and largest impact structure on the lunar surface and is most likely to crash through the lunar crust. However, remote sensing data obtained from existing lunar orbiters show that although the iron-magnesium mineral content of the SPA area is high, there is no evidence of widespread peridot exposure. Whether these substances may have originated from the mantle is controversial. China's Chang'e-4 probe recently landed in the von Kármán impact crater in the SPA area on the far side of the moon and carried out a patrol using the lunar rover, Yutu 2. Li Chunlai's research group and collaborators at the National Astronomical Observatory of the Chinese Academy of Sciences reported the preliminary spectral detection results of the visible and near-infrared spectrometer (VNIS) configured on Yutu 2, and the analysis found the presence of low-calcium (orthopedic) pyroxene and olivine, a mineral combination that most likely represents deep material originating from the lunar mantle. Further geological background analysis showed that the material was excavated from the nearby Finson impact crater with a diameter of 72 kilometers and ejected into 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 of the moon, and deepen the understanding of the formation and evolution of the lunar interior. Jade Rabbit 2 will continue to explore these materials at the bottom of Von Kármán Crater to understand their geological background, origin and composition, and to provide a basis for future lunar sample sampling and return missions.
02. Construct a heterogeneous chip for artificial general intelligence
There are generally two approaches to the development of artificial general intelligence (AGI): computer science-oriented or neuroscience-oriented, and combining the two is currently recognized as the best path to develop AGI. Because of their fundamentally different concepts and coding schemes, the two approaches rely on very different and incompatible computing platforms, making it very difficult to build an integrated computing platform that hinders the development of AGI. Therefore, it is important to develop a universal platform capable of supporting both popular computer science-based artificial neural networks and neuroscience-inspired models and algorithms. The Shi Luping Research Group of Tsinghua University and its collaborators proposed a tianji chip architecture, which efficiently integrates the above two methods and provides a heterogeneously integrated collaborative computing platform. The chip uses a mixed coding scheme with multi-core structure, reconfigurable components and streamlined data streams, which can independently support both computer science-based machine learning algorithms and neuroscience-led algorithms and multiple coding schemes in neuroscience, as well as supporting heterogeneous hybrid modeling of the two, providing new solutions. Using only one chip, the researchers demonstrated the synchronous processing of common algorithms and models in driverless bicycle systems, enabling real-time object detection, tracking, voice control, obstacle avoidance, obstacle crossing, and balance control. The study is expected to pave the way for more general-purpose hardware platform development and drive the development of AGI.
03. Propose an autoimmune disease treatment scheme based on enzyme regulation by DNA detection
There are thousands of viruses, and their infection characteristics and pathogenic methods are also ever-changing, but it is inseparable that when the virus invades, its own genetic material will inevitably be brought into the host cell. The body responds quickly to these exogenous genetic materials ( such as DNA ) , even at the expense of injuring itself , which is the main cause of lethal inflammation caused by viral infections. The understanding of the immune response induced by foreign DNA dates back hundreds of years, but the mechanism behind it is not clear. In 2013, an important international breakthrough was made in this field, when scientists identified the protein cGAS (cyclic guanylate-adenylate synthase) as an intracellular DNA virus receptor. As cGAS was revealed, scientists found that in addition to detecting viral invasions, abnormal activation of cGAS also directly leads to a class of autoimmune diseases. Therefore, finding effective means to control the activity of cGAS and exploring its regulatory mechanism are crucial for the treatment of anti-viral infections and autoimmune diseases. The research group of Zhang Xuemin and Li Tao of the Military Medical Research Institute (National Biomedical Analysis Center) and collaborators found that acetylation modification is a key molecular event that controls cGAS activity and reveals the regulatory laws behind it. The researchers identified three key acetylation sites of cGAS (K384, K394, and K414) and found that acetylation modifications at any of these sites can cause cGAS to become inactive. Further, the researchers found that acetylsalicylic acid (aspirin) can force cGAS to undergo acetylation at the above key sites to inhibit its activity. In addition, further exploration of the cGAS regulatory mechanism found that cGAS exists and functions in the form of complexes within the cell. The researchers used protein mass spectrometry to identify G3BP1, a key regulator of cGAS. Mechanism studies have revealed that G3BP1 binds to cGAS, ensuring that it can recognize DNA more efficiently by helping cGAS form polymers. In the absence of G3BP1, the activity of cGAS in cells is significantly reduced. Importantly, the natural small molecule compound EGCG, the main component of green tea polyphenols, is an inhibitor of G3BP1. The researchers found that EGCG was able to inhibit cGAS activation by interfering with G3BP1's interaction with cGAS. The above studies not only revealed the key regulatory mechanisms of the body's antiviral infection, but also found effective cGAS inhibitors, providing potential treatment strategies for autoimmune diseases such as AGS (Ekadi syndrome).
04. Crack the protein structure and function of underwater photosynthesis of algae
Photosynthesis uses sunlight to convert carbon dioxide and water into organic matter and oxygen, providing energy and oxygen for the survival of almost all living things on Earth. In order to adapt to different light environments, photosynthetic organisms have evolved a variety of different pigment molecules and pigment-binding proteins to maximize the use of light energy in different environments. Diatoms are a rich and important aquatic photosynthetic eukaryote, accounting for 40% of the productivity of aquatic organisms' primordial organic matter, or 20% of the total primordial productivity of the Earth, and play an important role in the global carbon cycle. One of the important factors in the successful reproduction of diatoms in aquatic environments is that it contains fucoxanthin/chlorophyll-binding membrane proteins (FCPs), which give diatoms a unique ability to capture and protect light and adapt quickly to changes in light intensity. The Shen Jianren and Kuang Tingyun Research Group of the Institute of Botany of the Chinese Academy of Sciences reported the high-resolution crystal structure of marine diatom-triangular brown finger algae FCP, revealing the detailed binding sites of 7 chlorophyll a, 2 chlorophyll c, 7 fucoxanthin and possible 1 diasilatecerin in the protein scaffold, thus revealing the efficient energy transmission pathway between chlorophyll a and c. The structure also shows the close interaction between fucoxanthin and chlorophyll, allowing energy to be efficiently transferred and quenched through fucoxanthin. The research team further collaborated with Sui Senfang's research group in the School of Life Sciences of Tsinghua University to analyze the cryo-EM structure of diatom's optical system II (PSII) and FCPII supercompos with a resolution of 3.0 angstroms. The supercomposite consists of two PSII-FCPII monomers, each containing a PSII core complex with 24 subunits and 11 peripheral FCPII antenna subunits, where the FCPII antennas exist as 2 FCPII tetramers and 3 FCPII monomers. The entire PSII-FCPII dimer contains 230 chlorophyll a molecules, 58 chlorophyll C molecules, 146 carotenoid molecules, as well as manganese cluster complexes, electron transporters and a large number of lipid molecules. This structure reveals the characteristics of the endemic subunits in the diatom PSII core and its obviously different antenna subunit arrangement from the higher plant PSII-LHCII complex, as well as the huge pigment distribution network of diatoms, providing a solid structural foundation for elucidating the efficient blue-green light capture, energy transfer and dissipation mechanisms of diatoms.
To further understand underwater photosynthesis, the researchers also analyzed the structure of the widely existing aquatic organism with similar photosynthesis to higher plants based on cryo-EM technology, the green algae (Pseudogenic plume) photosystem I (PSI)-photoretched complex I (LHCI) supercomplex, with a resolution of 3.49 angstroms. The structure reveals 13 PSI core subunits containing the characteristics of prokaryotes and eukaryotes subunits, as well as the structure of 10 LHCI antenna subunits (8 of which form a bicyclic structure and the remaining 2 form an additional LHCI dimer). In collaboration with Zhang Xing's research group at Zhejiang University School of Medicine, the cryo-EM structure of the complete C2S2M2N2 PSII-LHCII supercomplex of green algae-Rheinrich chlamydia was analyzed with a resolution of 3.37 angstroms. The structure shows that the green algae C2S2M2N2 supercomplex is a dimer, each monomer consists of a PSII core complex located in the center and 3 LHCII trimers, 1 CP26 and 1 CP29 peripheral antenna subunit surrounding the core. The work also revealed several structural features of the green algae PSII core and light-catching antenna LHCII that differ from those of higher plants. The above studies provide a solid structural basis for revealing the efficient absorption, transmission and quenching mechanisms of light energy in green algae, and provide important clues for revealing the changes that occur in the evolutionary process of PSI-LHCI and PSI-LHCII supramolecular complexes.
The above research progress has taken the lead in solving the mystery of the structure and function of supramolecular proteins of diatoms and green algae photosynthetic membrane proteins, which is of great significance not only to reveal the efficient transformation mechanism of photosynthesis in nature, but also to provide new ideas and strategies for artificially simulating photosynthesis, guiding the design of new crops, and building intelligent plant factories.
05. Based on material genetic engineering, high-temperature block metal glass was developed
Metal glass has a unique disordered atomic structure, so that it has excellent mechanical and physical and chemical properties, in energy, communications, aerospace, national defense and other high-tech fields have a wide range of applications, is an important part of modern alloy materials. Due to the plastic flow of metallic glass as it approaches the glass transition temperature, the mechanical strength is significantly reduced, severely limiting their high temperature applications. Although a metal glass with a glass transition temperature greater than 1000 K has been developed, due to its narrow supercooled liquid phase zone (the temperature range between the glass transition temperature and the crystallization temperature), its glass formation capacity is insufficient, and it is difficult to form a large-size material; and its thermoplastic performance is very poor, and it is difficult to process parts. The key to the above challenges lies in the rational design of the formation components of the metal glass, and the metal glass with specific properties found so far is mainly the result of repeated trials and attempts. Based on the concept of material genetic engineering, Liu Yanhui's research group and collaborators developed a high-throughput experimental method with high efficiency, non-destructiveness and easy generalization, designed an Ir-Ni-Ta-(B) alloy system, and obtained high-temperature block metal glass with a glass transition temperature of up to 1162 K. The newly developed metal glass has extremely high strength at high temperatures, with a strength of up to 3.7 gigapascals at 1000 K, far exceeding the previously reported block metal glass and traditional superalloys. The metal glass has an ultracooled liquid phase area of 136 K, which is wider than most previously reported metal glass, and its forming capacity can reach 3 mm, allowing it to obtain small-scale parts for application at high temperatures or harsh environments through thermoplastic molding. The high-throughput experimental method developed by this research and development has strong practicality, subverts the material research and development mode of "stir-fry" in the field of metal glass for 60 years, confirms the effectiveness and high efficiency of material genetic engineering in the research and development of new materials, opens up new ways to solve the problem of efficient exploration of new materials for metal glass, and also provides new ideas for the design of new high-temperature and high-performance alloy materials.
06. Elucidate the mechanism of europium ions to improve the life of perovskite solar cells
Perovskite solar cells are a new generation of photovoltaic technology that has attracted widespread attention, and its working stability is the main obstacle to industrialization at present. Traditional research mainly uses component optimization, packaging, interface modification and UV light filtering to effectively suppress the performance degradation caused by factors such as oxygen, moisture and UV light, thereby improving the stability of the device. However, to further improve the lifetime of the device, a long-term effective method needs to be developed to suppress the intrinsic defects of the material during the service process. In order to improve the eigen-stability, the Zhou Huanping Research Group of the School of Engineering of Peking University, the Yan Chunhua/Sun Lingdong Research Group of the School of Chemistry and Molecular Engineering, and their collaborators proposed that by introducing a europium ion pair (Eu3+/Eu2+) in the perovskite active layer as a "redox shuttle", Pb0 and I0 defects can be eliminated at the same time, thereby greatly improving the service life of the device. Interestingly, the pair of ions is not significantly consumed during device use, and the corresponding device has an efficiency of up to 21.52% (certified value of 20.52%), and there is no significant hysteresis. At the same time, the thin film device introducing europium ion pairs exhibits excellent thermal stability and light stability, and the device can still maintain 91% and 89% of the original efficiency after continuous sunlight or 85oC heating for 1000 hours, respectively, and maintain 91% of the original efficiency after 500 hours of continuous operation at the maximum power point. This method solves an important essential factor limiting the stability of lead-halide perovskite solar cells, which can be generalized to other perovskite optoelectronic devices, and also has reference significance for other inorganic semiconductor devices facing similar problems.
07. Denisovans found on the Tibetan Plateau
The Denisovans are a mysterious ancient human that has disappeared, and the past knowledge of them is mainly based on a small number of fossil fragments unearthed only from the Denisova Cave in Siberia and the high-quality ancient genetic information preserved in them. Genetic studies have shown that Denisovans have made genetic contributions to some modern low-altitude East Asian populations and high-altitude modern Tibetan populations, and are of great significance for the adaptation of modern Tibetan populations to high-altitude environments. The lack of fossil morphological information makes it difficult for scientists to assess the connection between Denisovans and the abundance of paleoanthropology scattered across Asia and beyond, and to accurately understand the relationship of Denisovans to modern Asian populations. In addition, the genetic source of high-altitude environmental adaptation unique to modern Tibetans and other Tibetan Plateau populations, especially whether it is inherited from the Denisovans, is a very important and urgent scientific problem to be solved. Collaborators such as Chen Fahu of the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, Zhang Dongju of Lanzhou University, and Jean-Jacques Hublin Of the Institute of Evolutionary Anthropology of the Max Planck Society in Germany reported a mandible identified as Denisovan by paleoprotein analysis methods, which came from the Baishiya Cave in Xiahe County, Gansu Province, China. The researchers determined that the mandible was at least 160,000 years old by dating the carbonate nodules attached to the fossils by uranium dating. The fossil specimen is the first denisovan fossil evidence found outside of Denisova Cave, and a comprehensive analysis of the specimen also provides a wealth of physical morphology information for Denisovan studies, including information such as jaw and tooth morphology. The study shows that long before the arrival of modern Homo sapiens, denisovans lived at high altitudes on the Tibetan Plateau in the late Mesozoic period and successfully adapted to the cold and hypoxia environment.
08. Satellite test of gravitationally 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 and general relativity encounters great difficulties. There are many models in the current discussion of how to fuse quantum mechanics and gravitational theory, but there is a general lack of experimental testing. Pan Jianwei of the University of Science and Technology of China and his colleagues Peng Chengzhi and Fan Jingyun and other collaborators used the "Mozi" quantum science experimental satellite to carry out the experimental test of gravitational induced quantum entanglement decoherence in space in the world, and tested the decoherence of quantum entangled photons through the earth's gravitational field. According to the "event form" theory model, the correlation of entangled photon pairs propagating in the Earth's gravitational field will be probabilistically lost; according to existing quantum mechanical theories, all entangled photon pairs will maintain entanglement characteristics. Ultimately, the results of the satellite experiment do not support the predictions of the "event form" theoretical model, but are consistent with standard quantum theory. This is the first time in the world that quantum satellites have been used to conduct experimental tests on the theories that try to integrate quantum mechanics and general relativity in the earth's gravitational field, which will greatly promote the basic theories and experimental research of related physics.
09. Reveal the structure of African swine fever virus and its assembly mechanism
African swine fever virus (ASFV) is a huge and complex DNA virus, which can cause domestic pigs and wild boars to suffer from acute, hot, highly infectious diseases, morbidity and mortality rates can be as high as 100%, causing huge economic losses to the pig breeding industry chain, and there is no vaccine available. The team of Rao Zihe/Wang Xiangxi of the Institute of Biophysics of the Chinese Academy of Sciences and the Bu Zhigao team of the Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, together with Shanghai University of Science and Technology and other units, continuously collected high-quality data at the Cryo-EM Center of the University of Shanghaitech, and used an optimized image reconstruction strategy to analyze the three-dimensional structure of the capsid of African swine fever virus, with a resolution of 4.1 angstroms. The capsid particles are large and complex in structure, consisting of 17,280 protein subunits, including 1 primary (p72) and 4 secondary capsid proteins (M1249L, p17, p49 and H240R), which are assembled into a composite structure of five-fold symmetry and triple symmetry. The predominant capsid protein p72 atomic resolution structure exhibits a potential conformational antigen epitope of African swine fever virus, which is significantly different from other nuclear cytoplasmic large DNA viruses (NCLDV). Secondary capsid proteins form a complex network of protein interactions on the inner surface of the capsid, mediating the assembly of the capsid and stabilizing the structure of the capsid by regulating the forces between adjacent viral shell microsomes. As the core organizer, the 100-nanometer-long M1249L protein bridges two adjacent five-fold symmetries along each edge of the triple symmetry, forming an extended intermolecular network with other capsid proteins that drive the formation of the capsid framework. These structural details reveal the molecular basis of capsid stability and assembly, which is of great theoretical guidance for the development of African swine fever vaccines.
10. The three-dimensional quantum Hall effect was observed for the first time
The discovery of the quantum Hall effect in two-dimensional electronic systems allows topology to play a central role in condensed matter physics. More than 30 years ago, Bertrand Halperin et al. theoretically predicted the possibility of a quantum Hall effect in a three-dimensional electronic 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 of southern University of Science and Technology, the research group of Qiao Zhenhua of the Department of Physics of the University of Science and Technology of China, and Yang Shengyuan of the Singapore University of Science and Technology design cooperated to achieve the "three-dimensional quantum Hall effect" for the first time in the block zirconium telluride (ZrTe5) crystal. The researchers made low-temperature electron transport measurements of zirconium telluride single crystals under a magnetic field, reaching an extreme quantum limit state (only the lowest landau energy level was occupied) at a relatively low magnetic field. In this state, the researchers observed a dissipative longitudinal resistance close to zero and formed a good Platform of Hall resistance proportional to half a Fermi wavelength along the magnetic field, which is a conclusive sign of the emergence of a three-dimensional Hall effect. Theoretical analysis also shows that this effect stems from the instability of the Fermi surface driven by the charge density wave generated by electron correlation enhancement at extreme quantum limits. 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 of the three-dimensional quantum Hall effect and provides a promising platform for further exploration of exotic quantum phases and their phase transitions in three-dimensional electronic systems.
The selection activity of "Ten Advances in Chinese Science" is led by the High Technology Research and Development Center (Basic Research Management Center) of the Ministry of Science and Technology, and has been successfully held for 15 sessions so far, aiming to publicize the scientific progress of major basic research in China, stimulate the scientific enthusiasm and dedication of the major scientific and technological workers, carry out the popularization of basic research science, promote public understanding, care and support for basic research, and create a good scientific atmosphere in the whole society.
The selection process of the Top Ten Progress in Chinese Science is divided into three links: recommendation, primary selection and final selection. In 2019, five editorial departments, including China Basic Science, Science and Technology Herald, Journal of the Chinese Academy of Sciences, China Science Foundation and Science Bulletin, recommended a total of 320 scientific research progress, and the recommended scientific progress was officially published between December 1, 2018 and November 30, 2019.
In December 2019, the High Technology Research and Development Center (Basic Research Management Center) of the Ministry of Science and Technology organized and held the 2019 Annual Preliminary Selection Meeting of the Top Ten Advances in Chinese Science, which was divided into four discipline groups including mathematical and astronomical sciences, chemistry and materials science, earth and environmental sciences, and life and medical sciences according to the distribution of recommended scientific progress, and invited experts to select 30 progresses from the recommended scientific progress to enter the final selection. More than 2,600 experts and scholars, including academicians of the Chinese Academy of Sciences, academicians of the Chinese Academy of Engineering, directors of the State Key Laboratory, experts and project leaders of the overall expert group of some national key research and development programs, were invited to vote online on 30 candidate scientific progresses, and the top 10 scientific progresses with the top 10 votes were selected as the "Top Ten Advances in Chinese Science in 2019".