In this paper,a deep collocation method(DCM)for thin plate bending problems is proposed.This method takes advantage of computational graphs and backpropagation algorithms involved in deep learning.Besides,the proposed...In this paper,a deep collocation method(DCM)for thin plate bending problems is proposed.This method takes advantage of computational graphs and backpropagation algorithms involved in deep learning.Besides,the proposed DCM is based on a feedforward deep neural network(DNN)and differs from most previous applications of deep learning for mechanical problems.First,batches of randomly distributed collocation points are initially generated inside the domain and along the boundaries.A loss function is built with the aim that the governing partial differential equations(PDEs)of Kirchhoff plate bending problems,and the boundary/initial conditions are minimised at those collocation points.A combination of optimizers is adopted in the backpropagation process to minimize the loss function so as to obtain the optimal hyperparameters.In Kirchhoff plate bending problems,the C^1 continuity requirement poses significant difficulties in traditional mesh-based methods.This can be solved by the proposed DCM,which uses a deep neural network to approximate the continuous transversal deflection,and is proved to be suitable to the bending analysis of Kirchhoff plate of various geometries.展开更多
On May 21,2021,a local case of coronavirus disease 2019(COVID-19)was confirmed in a 75-year-old woman(experienced onset of symptoms on May 18)in Liwan District,Guangzhou City,Guangdong Province,China.The number of inf...On May 21,2021,a local case of coronavirus disease 2019(COVID-19)was confirmed in a 75-year-old woman(experienced onset of symptoms on May 18)in Liwan District,Guangzhou City,Guangdong Province,China.The number of infections has increased in the following 10 days and led to 5 generations of transmission.展开更多
Cholellthiasis is a kind of common and multiple diseases. In recent years, traolttonal laparommy has been challenged by a minimally invasive surgery. Through literature review, the therapeutic method, effect, and comp...Cholellthiasis is a kind of common and multiple diseases. In recent years, traolttonal laparommy has been challenged by a minimally invasive surgery. Through literature review, the therapeutic method, effect, and complications of minimally invasive treatment of intrahepatic and extrahepatic bile duct stones by combining our practical experience were summarized as follows. （1） For intrahepatic bile duct stones, the operation may be selected by laparoscopie liver resection, laparoscopic common bile duct exploration （LCBDE）, or percutaneous transhepatic cholangioscopy. （2） For concomitant gallstones and common bile duct stones, the surgical approach can be selected as follows： laparoscopic cholecystectomy （LC） combined with endoscopic sphincterotomy （EST） or endoscopic papillary balloon dilatation, LC plus laparoscopic transcystic common bile duct exploration, LC plus LCBDE, and T-tube drainage or primary suture. （3） For concomitant intrahepatic and extrahepatic bile duct stones, laparoscopic liver resection, choledochoscopy through the hepatic duct orifice on the hepatectomy cross section, LCBDE, EST, and percutaneous transhepatic cholangioscopic lithotripsy could be used. According to the abovementioned principle, the minimally invasive treatment approach combined with the surgical technique and equipment condition will be significant in improving the therapeutic effect and avoiding the postoperative complications or hidden dangers of intrahepatic and extrahepatic bile duct stones.展开更多
To identify useful genes from wild rice which have been lost or weakened in cultivated rice has become more and more important for modern breeding strategy. In this study, a BC4 population derived from 94W1, an access...To identify useful genes from wild rice which have been lost or weakened in cultivated rice has become more and more important for modern breeding strategy. In this study, a BC4 population derived from 94W1, an accession of common wild rice (Oryza rufipogon Griff.) from Dongxiang in Jiangxi Province of China, as the donor, and a high-yielding Indica cultivar (O. sativa L.), 'Guichao 2', as the recipient, was used to identify quantitative trait loci (QTL) associated with yield and its components. Based on the analysis for the genotype of BC4F1 population with 87 SSR markers distributed throughout the genome and investigation of the plant height, yield and yield components of BC4F2, a total of 52 QTLs, were detected. Of 7 QTLs associated with grain yield per plant, 2 QTLs on chromosome 2 and chromosome 11 for grain yield, explaining 16% and 11% of the phenotypic variance respectively, were identified. The alleles from Dongxiang common wild rice in those two loci could increase the yield of 'Guichao 2' by展开更多
Two-dimensional materials having a layered structure comprise a monolayer or multilayers of atomic thickness and ultra-low shear strength.Their high specific surface area,in-plane strength,weak layer-layer interaction...Two-dimensional materials having a layered structure comprise a monolayer or multilayers of atomic thickness and ultra-low shear strength.Their high specific surface area,in-plane strength,weak layer-layer interaction,and surface chemical stability result in remarkably low friction and wear-resisting properties.Thus,2D materials have attracted considerable attention.In recent years,great advances have been made in the scientific research and industrial applications of anti-friction,anti-wear,and lubrication of 2D materials.In this article,the basic nanoscale friction mechanisms of 2D materials including interfacial friction and surface friction mechanisms are summarized.This paper also includes a review of reports on lubrication mechanisms based on the film-formation,self-healing,and ball bearing mechanisms and applications based on lubricant additives,nanoscale lubricating films,and space lubrication materials of 2D materials in detail.Finally,the challenges and potential applications of 2D materials in the field of lubrication were also presented.展开更多
β-Thalassemia is a global health issue, caused by mutations in the HBB gene. Among these mutations, HBB -28 （A〉G） mutations is one of the three most common mutations in China and Southeast Asia patients with β-th...β-Thalassemia is a global health issue, caused by mutations in the HBB gene. Among these mutations, HBB -28 （A〉G） mutations is one of the three most common mutations in China and Southeast Asia patients with β-thalassemia. Correcting this mutation in human embryos may prevent the disease being passed onto future generations and cure anemia. Here we report the first study using base editor （BE） system to correct disease mutant in human embryos. Firstly, we produced a 293T cell line with an exogenous HBB -28 （A〉G） mutant fragment for gRNAs and targeting efficiency evaluation. Then we collected primary skin fibroblast cells from a β-thalassemia patient with HBB -28 （A〉G） homozygous mutation. Data showed that base editor could precisely correct HBB -28 （A〉G） mutation in the patient＇s primary cells. To model homozygous mutation disease embryos, we consb＇ucted nuclear transfer embryos by fusing the lymphocyte or skin fibroblast cells with enucleated in vitro matured （IVM） oocytes.Notably, the gene correction efficiency was over 23.0% in these embryos by base editor. Although these embryos were still mosaic, the percentage of repaired blastomeres was over 20.0%. In addition, we found that base editor variants, with narrowed deamination window, could promote G-to-A conversion at HBB -28 site precisely in human embryos. Collectively, this study demonstrated the feasibility of curing genetic disease in human somatic cells and embryos by base editor system.展开更多
The 2021 Qinghai Maduo M_(S)7.4 earthquake was one of the strongest earthquakes that occurred in the Bayan Har block of the Tibetan Plateau during the past 30 years,which spatially filled in the gap of strong earthqua...The 2021 Qinghai Maduo M_(S)7.4 earthquake was one of the strongest earthquakes that occurred in the Bayan Har block of the Tibetan Plateau during the past 30 years,which spatially filled in the gap of strong earthquake in the eastern section of the northern block boundary.In this study,the aftershock sequence within 8 days after the mainshock was relocated by double difference algorithm.The results show that the total length of the aftershock zone is approximately 170 km;the mainshock epicenter is located in the center of the aftershock zone,indicating a bilateral rupture.The aftershocks are mainly distributed along NWW direction with an overall strike of 285°.The focal depth profiles indicate that the seismogenic fault is nearly vertical and dips to southwest or northeast in different sections,indicating a complex geometry.There is an aftershock gap located to the southeast of the mainshock epicenter with a scale of approximately 20 km.At the eastern end of the aftershock zone,horsetaillike branch faults show the terminal effect of a large strike-slip fault.There is a NW-trending aftershock zone on the north side of the western section,which may be a branch fault triggered by the mainshock.The location of the aftershock sequence is close to the eastern section of the Kunlun Mountain Pass-Jiangcuo(KMPJ)fault.The sequence overlaps well with surface trace of the KMPJ fault.We speculate that the KMPJ fault is the main seismogenic fault of the M_(S)7.4 Maduo earthquake.展开更多
High-quality reservoirs occur in the middle-shallow horizons of the northern Songliao Basin. The distribution and genesis of their anomalously high porosity zones were studied using measured porosities, examination of...High-quality reservoirs occur in the middle-shallow horizons of the northern Songliao Basin. The distribution and genesis of their anomalously high porosity zones were studied using measured porosities, examination of ordinary thin sections and blue epoxy resin-impregnated thin sections and by SEM. The results show that there are three anomalously high porosity zones at the depth of 450-900 m, 1,300-1,900 m, 2,050-2,350 m respectively, named zone i, zone ii and zone iii from top to bottom. Horizontally, zone i and zone ii are distributed all over the basin except in the Southeastern Uplift, while zone iii is only distributed in the Central Depression. Zone i was formed by meteoric water leaching as well as organic acid dissolution. Zones ii and iii were dominantly formed by organic acid dissolution. Additionally, clay mineral transformation generating H＋ and hydrocarbon emplacement retarding the cementation of sandstones are also important for the formation of zones ii and iii.展开更多
An in situ chemical synthesis approach has been employed to prepare an Ag-chemically converted graphene (CCG) nanocomposite. The reduction of graphene oxide sheets was accompanied by generation of Ag nanoparticles. Th...An in situ chemical synthesis approach has been employed to prepare an Ag-chemically converted graphene (CCG) nanocomposite. The reduction of graphene oxide sheets was accompanied by generation of Ag nanoparticles. The structure and composition of the nanocomposites were confirmed by means of transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray diffraction. TEM and AFM results suggest a homogeneous distribution of Ag nanoparticles (5-10 nm in size) on CCG sheets. The intensities of the Raman signals of CCG in such nanocomposites are greatly increased by the attached silver nanoparticles, i.e., there is surface-enhanced Raman scattering activity. In addition, it was found that the antibacterial activity of free Ag nanoparticles is retained in the nanocomposites, which suggests they can be used as graphene-based biomaterials.展开更多
Background:The long-term trend in cancer death in a rapidly developing country provides information for cancer prophylaxis.Here,we aimed to identify the trends in cancer mortality in China during the 2004-2018 period....Background:The long-term trend in cancer death in a rapidly developing country provides information for cancer prophylaxis.Here,we aimed to identify the trends in cancer mortality in China during the 2004-2018 period.Methods:Using raw data from the national mortality surveillance system of China,we assessed the mortalities of all cancer and site-specific cancers during the 2004-2018 period.The participants were divided into three age groups:≥65 years,40-64 years,and≤39 years.Changing trends in cancer death by gender,residency,and tumor location were estimated using fitting joinpoint models to log-transformed crude mortality rates(CMRs)and age-standardizedmortality rates(ASMRs).Results:Cancer death accounted for 24% of all-cause of death in China during 2014-2018.The CMR of all cancer was 150.0 per 100,000 persons.Cancer was the leading cause of death in the population<65 years.The six major cancer types(lung/bronchus cancer,liver cancer,stomach cancer,esophagus cancer,colorectal cancer,and pancreas cancer)accounted for 75.85% of all cancer deaths.The CMR of all cancer increased while the ASMR decreased during 2014-2018(P<0.001).Lung/bronchus cancer and liver cancer were the leading causes of cancer death in the population<65 years,accounting for 45.31%(CMR)and 44.35%(ASMR)of all cancer death,respectively.The ASMR of liver cancer was higher in the 40-64 years population than in the≥65 years population,in contrast to the other five major cancers.The ASMRs of liver cancer,stomach cancer,and esophagus cancer decreased although they were higher in rural residents than in urban residents;the ASMRs of lung/bronchus cancer,colorectal cancer,and pancreas cancer increased in rural residents although they were higher in urban residents than in rural residents during 2014-2018.Conclusion:Although the ASMR of all cancer decreased in China during 2004-2018,lung/bronchus cancer and liver cancer remained the leading causes of cancer-related premature death.Lung/bronchus cancer,colorectal cancer,and pancreas cancer increase展开更多
Soil salinity is one of the major abiotic stresses affecting plant growth and crop production.In the present study,salt tolerance at rice seedling stage was evaluated using 87 introgression lines（ILs）,which were der...Soil salinity is one of the major abiotic stresses affecting plant growth and crop production.In the present study,salt tolerance at rice seedling stage was evaluated using 87 introgression lines（ILs）,which were derived from a cross between an elite indica cultivar Teqing and an accession of common wild rice（Oryza rufipogon Griff.）.Substantial variation was observed for four traits including salt tolerance score（STS）, relative root dry weight（RRW）,relative shoot dry weight（RSW） and relative total dry weight（RTW）.STS was significantly positively correlated with all other three traits.A total of 15 putative quantitative trait loci（QTLs） associated with these four traits were detected using single-point analysis,which were located on chromosomes 1,2,3,6,7,9 and 10 with 8%-26%explaining the phenotypic variance.The O. rufipogon-derived alleles at 13 QTLs（86.7%） could improve the salt tolerance in the Teqing background.Four QTL clusters affecting RRW, RSW and RTW were found on chromosomes 6,7,9 and 10,respectively.Among these four QTL clusters,a major cluster including three QTLs （qRRWIO,qRSWIO and qRTWIO） was found near the maker RM271 on the long arm of chromosome 10,and the O.rufipogon-derived alleles at these three loci increased RRW,RSW and RTW with additive effects of 22.7%,17.3%and 18.5%,respectively,while the phenotypic variance explained by these three individual QTLs for the three traits varied from 19%to 26%.In addition,several salt tolerant ILs were selected and could be used for identifying and utilizing favorable salt tolerant genes from common wild rice and used in the salt tolerant rice breeding program.展开更多
A few species in the genus Grateloupia （Halymeniaceae, Rhodophyta） have been investigated in detail with respect to morphological observations and molecular analyses. In this study, the au- thors document the vegeta...A few species in the genus Grateloupia （Halymeniaceae, Rhodophyta） have been investigated in detail with respect to morphological observations and molecular analyses. In this study, the au- thors document the vegetative and reproductive structures of two new species of Grateloupia, G. dalianensis H.W.Wang et D.Zhao, sp.nov, and G. yinggehaiensis H.W.Wang et R.X.Luan, sp.nov. They both have the morphological character that carpogonial ampullae and auxiliary cell ampullae are the simple Grateloupia-type. The two species can be distinguished from other species of the genus by their distinctive morphological features respectively. Bused on ribulose-l,5-bisphosphate carboxylase/oxygenase （rbcL） gene sequences, the phylogenetic tree obtained in the study indicated that they are both embedded within the Grateloupia clade. G. dalianensis clusters a subclade with G. asiatica, and G. yinggehaiensis forms a single monophyletic subclade with G. hawaiiana.展开更多
A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well-defined structures and propert...A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well-defined structures and properties have been synthesized, and many more are theoretically predicted to exist. Due to the numerous assets including excellent mechanical properties, metallic conductivity,unique in-plane anisotropic structure, tunable band gap, and so on, MXenes rapidly positioned themselves at the forefront of the 2D materials world and have found numerous promising applications. Particular interest is devoted to applications in electrochemical energy storage, whereby 2D MXenes work either as electrodes,additives, separators, or hosts. This review summarizes recent advances in the synthesis, fundamental properties and composites of MXene and highlights the state-of-the-art electrochemical performance of MXene-based electrodes/devices.The progresses in the field of supercapacitors and Li-ion batteries, Li-S batteries, Naand other alkali metal ion batteries are reviewed, and current challenges and new opportunities for MXenes in this surging energy storage field are presented. In the focus of interest is the possibility to boost device-level performance, particularly that of rechargeable batteries, which are of utmost importance in future energy technologies. Very recently, the 2019 Nobel Prize in Chemistry was awarded to the inventors of the Li-ion battery. For sure, this will provide an additional stimulation to study fundamental aspects of electrochemical energy storage.展开更多
Flowering at suitable time is very important for plants to adapt to complicated environments and produce their seeds successfully for reproduction. In rice （Oryza rufipogon Griff.） photoperiod regulation is one of t...Flowering at suitable time is very important for plants to adapt to complicated environments and produce their seeds successfully for reproduction. In rice （Oryza rufipogon Griff.） photoperiod regulation is one of the important factors for controlling heading date. Common wild rice, the ancestor of cultivated rice, exhibits a late heading date and a more sensitive photoperiodic response than cultivated rice. Here, through map-based cloning, we identified a major quantitative trait loci （QTL） LHD1 （Late Heading Date 1）, an allele of DTH8/Ghd8, which controls the late heading date of wild rice and encodes a putative HAP3/NF-YB/CBF-A subunit of the CCAAT-box-binding transcription factor. Sequence analysis revealed that several variants in the coding region of LHD1 were correlated with a late heading date, and a further complementary study successfully rescued the phenotype. These results suggest that a functional site for LHD1 could be among those variants present in the coding region. We also found that LHD1 could down-regulate the expression of several floral transition activators such as Ehdl, Hd3a and RFT1 under long-day conditions, but not under short-day conditions. This indicates that LHD1 may delay flowering by repressing the expression of Ehdl, Hd3a and RFT1 under long-day conditions.展开更多
A two-stage upflow anaerobic sludge blanket （UASB） and sequencing batch reactor （SBR） system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to impro...A two-stage upflow anaerobic sludge blanket （UASB） and sequencing batch reactor （SBR） system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen （TN） removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB （UASB1） to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/（m^3.day）, respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^＋-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^＋-N removal efficiency at relatively low temperature （14.9-10.9℃）. More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^＋-N once the complete nitrification and denitrification were achieved.展开更多
Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de n...Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de novo assembled 816-Mb high-quality,chromosome-level haploid genome sequence for‘Zhongmu No.1’alfalfa,a heterozygous autotetraploid.The contig N50 is 3.92 Mb,and 49165 genes are annotated in the genome.The alfalfa genome is estimated to have diverged from M.truncatula approximately 8 million years ago.Genomic population analysis of 162 alfalfa accessions revealed high genetic diversity,weak population structure,and extensive gene flow from wild to cultivated alfalfa.Genome-wide association studies identified many candidate genes associated with important agronomic traits.Furthermore,we showed that MsFTa2,a Flowering Locus T homolog,whose expression is upregulated in salt-resistant germplasms,may be associated with fall dormancy and salt resistance.Taken together,these genomic resources will facilitate alfalfa genetic research and agronomic improvement.展开更多
Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in ...Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in this study. The measured fission track apparent ages, combined with the simulated annealing mod- eling of the thermal history, have been used to reconstruct the thermal evolutionary histories of the samples and interpret the active history of the thrusts and faults in these areas. Thermal history mod- eling shows that earlier tectonic cooling occurred in the Garzê-Litang thrust in Miocene (~20―16 Ma) whereas the later cooling occurred mainly in the Longmen Shan thrust since ~5 Ma. Our study sug- gests that the margin of eastern Tibetan Plateau was extended by stages: through strike-slip faults deformations and related thrusts, the upper crust formed the Garzê-Litang margin in the Miocene epoch and then moved to the Longmen Shan margin since ~5 Ma. During this process, the deformations of different phases in the eastern Tibetan Plateau were absorbed by the thrusts within them and conse- quently the tectonic events of long-distance slip and extrusion up to hundreds of kilometers have not been found.展开更多
The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that ...The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.展开更多
With the widespread application of radionuclide ^235U（VI）, it is inevitable that part of U（VI） is released into the natural environment. The potential toxicity and irreversibility impact on the natural environment...With the widespread application of radionuclide ^235U（VI）, it is inevitable that part of U（VI） is released into the natural environment. The potential toxicity and irreversibility impact on the natural environment has become one of the most forefront pollution problems in nuclear energy utilization. In this work, rod-like metal-organic framework （MOF-5） nanomaterial was synthesized by a solvothermal method and applied to efficiently adsorb U（VI） from aqueous solutions. The batch experimental results showed that the sorp- tion of U（Vl） on MOF-5 was strongly dependent on pH and independent of ionic strength, indicating that the dominant interaction mechanism was inner-sphere surface complexation and electrostatic interac- tion. The maximum sorption capacity of U（Vl） on MOF-5 was 237.0 mg]g at pH 5.0 and T = 298 K, and the sorption equilibrium reached within 5 rain. The thermodynamic parameters indicated that the removal of U（VI） on MOF-5 was a spontaneous and endothermic process. Additionally, the FT-IR and XPS analyses implied that the high sorption capacity of U（Vl） on MOF-5 was mainly attributed to the abundant oxygen-containing functional groups （i.e., C-O and C=O）. Such a facile preparation method and efficient removal performance highlighted the application of MOF-5 as a candidate for rapid and efficient radionuclide contamination＇s elimination in practical applications.展开更多
文摘In this paper,a deep collocation method(DCM)for thin plate bending problems is proposed.This method takes advantage of computational graphs and backpropagation algorithms involved in deep learning.Besides,the proposed DCM is based on a feedforward deep neural network(DNN)and differs from most previous applications of deep learning for mechanical problems.First,batches of randomly distributed collocation points are initially generated inside the domain and along the boundaries.A loss function is built with the aim that the governing partial differential equations(PDEs)of Kirchhoff plate bending problems,and the boundary/initial conditions are minimised at those collocation points.A combination of optimizers is adopted in the backpropagation process to minimize the loss function so as to obtain the optimal hyperparameters.In Kirchhoff plate bending problems,the C^1 continuity requirement poses significant difficulties in traditional mesh-based methods.This can be solved by the proposed DCM,which uses a deep neural network to approximate the continuous transversal deflection,and is proved to be suitable to the bending analysis of Kirchhoff plate of various geometries.
基金The Key-Area Research and Development Program of Guangdong Province(2019B111103001,2020B111107001)The National Natural Science Foundation of China(No.82041030).
文摘On May 21,2021,a local case of coronavirus disease 2019(COVID-19)was confirmed in a 75-year-old woman(experienced onset of symptoms on May 18)in Liwan District,Guangzhou City,Guangdong Province,China.The number of infections has increased in the following 10 days and led to 5 generations of transmission.
文摘Cholellthiasis is a kind of common and multiple diseases. In recent years, traolttonal laparommy has been challenged by a minimally invasive surgery. Through literature review, the therapeutic method, effect, and complications of minimally invasive treatment of intrahepatic and extrahepatic bile duct stones by combining our practical experience were summarized as follows. （1） For intrahepatic bile duct stones, the operation may be selected by laparoscopie liver resection, laparoscopic common bile duct exploration （LCBDE）, or percutaneous transhepatic cholangioscopy. （2） For concomitant gallstones and common bile duct stones, the surgical approach can be selected as follows： laparoscopic cholecystectomy （LC） combined with endoscopic sphincterotomy （EST） or endoscopic papillary balloon dilatation, LC plus laparoscopic transcystic common bile duct exploration, LC plus LCBDE, and T-tube drainage or primary suture. （3） For concomitant intrahepatic and extrahepatic bile duct stones, laparoscopic liver resection, choledochoscopy through the hepatic duct orifice on the hepatectomy cross section, LCBDE, EST, and percutaneous transhepatic cholangioscopic lithotripsy could be used. According to the abovementioned principle, the minimally invasive treatment approach combined with the surgical technique and equipment condition will be significant in improving the therapeutic effect and avoiding the postoperative complications or hidden dangers of intrahepatic and extrahepatic bile duct stones.
基金This work was supported by the "973" Project (Grant No. 2001CB108800)China National High-Tech Research and Development Program ("863" Program)the National Tackle Key Problem Project of the Ministry of Science and Technology of China.
文摘To identify useful genes from wild rice which have been lost or weakened in cultivated rice has become more and more important for modern breeding strategy. In this study, a BC4 population derived from 94W1, an accession of common wild rice (Oryza rufipogon Griff.) from Dongxiang in Jiangxi Province of China, as the donor, and a high-yielding Indica cultivar (O. sativa L.), 'Guichao 2', as the recipient, was used to identify quantitative trait loci (QTL) associated with yield and its components. Based on the analysis for the genotype of BC4F1 population with 87 SSR markers distributed throughout the genome and investigation of the plant height, yield and yield components of BC4F2, a total of 52 QTLs, were detected. Of 7 QTLs associated with grain yield per plant, 2 QTLs on chromosome 2 and chromosome 11 for grain yield, explaining 16% and 11% of the phenotypic variance respectively, were identified. The alleles from Dongxiang common wild rice in those two loci could increase the yield of 'Guichao 2' by
基金supported by the National Natural Science Foundation of China(Grant No.51505442)Guangxi Natural Science Foundation(Grant No.2018GXNSFAA138174)
文摘Two-dimensional materials having a layered structure comprise a monolayer or multilayers of atomic thickness and ultra-low shear strength.Their high specific surface area,in-plane strength,weak layer-layer interaction,and surface chemical stability result in remarkably low friction and wear-resisting properties.Thus,2D materials have attracted considerable attention.In recent years,great advances have been made in the scientific research and industrial applications of anti-friction,anti-wear,and lubrication of 2D materials.In this article,the basic nanoscale friction mechanisms of 2D materials including interfacial friction and surface friction mechanisms are summarized.This paper also includes a review of reports on lubrication mechanisms based on the film-formation,self-healing,and ball bearing mechanisms and applications based on lubricant additives,nanoscale lubricating films,and space lubrication materials of 2D materials in detail.Finally,the challenges and potential applications of 2D materials in the field of lubrication were also presented.
基金We are grateful to Dr. Qi Zhou for helpful suggestions. This work was supported by National Key R＆D Program of China （2017YFC1001901 and 2017YFC1001600）, the Science and Technology Planning Project of Guangdong Province （2015B020228002）, the Guangzhou Science and Technology Project （201707010085） and the National Natural Science Foundation of China （Grant No. 81771579）.
文摘β-Thalassemia is a global health issue, caused by mutations in the HBB gene. Among these mutations, HBB -28 （A〉G） mutations is one of the three most common mutations in China and Southeast Asia patients with β-thalassemia. Correcting this mutation in human embryos may prevent the disease being passed onto future generations and cure anemia. Here we report the first study using base editor （BE） system to correct disease mutant in human embryos. Firstly, we produced a 293T cell line with an exogenous HBB -28 （A〉G） mutant fragment for gRNAs and targeting efficiency evaluation. Then we collected primary skin fibroblast cells from a β-thalassemia patient with HBB -28 （A〉G） homozygous mutation. Data showed that base editor could precisely correct HBB -28 （A〉G） mutation in the patient＇s primary cells. To model homozygous mutation disease embryos, we consb＇ucted nuclear transfer embryos by fusing the lymphocyte or skin fibroblast cells with enucleated in vitro matured （IVM） oocytes.Notably, the gene correction efficiency was over 23.0% in these embryos by base editor. Although these embryos were still mosaic, the percentage of repaired blastomeres was over 20.0%. In addition, we found that base editor variants, with narrowed deamination window, could promote G-to-A conversion at HBB -28 site precisely in human embryos. Collectively, this study demonstrated the feasibility of curing genetic disease in human somatic cells and embryos by base editor system.
基金supported by the National Key R&D Program of China(Grant No.2018YFC1504103)the National Natural Science Foundation of China(Grant No.41774067)+1 种基金the Special Fund of the Institute of Geophysics,China Earthquake Administration(Grant No.DQJB20X07)S&T Program of Qinghai Province(Grant No.2020-ZJ-752).
文摘The 2021 Qinghai Maduo M_(S)7.4 earthquake was one of the strongest earthquakes that occurred in the Bayan Har block of the Tibetan Plateau during the past 30 years,which spatially filled in the gap of strong earthquake in the eastern section of the northern block boundary.In this study,the aftershock sequence within 8 days after the mainshock was relocated by double difference algorithm.The results show that the total length of the aftershock zone is approximately 170 km;the mainshock epicenter is located in the center of the aftershock zone,indicating a bilateral rupture.The aftershocks are mainly distributed along NWW direction with an overall strike of 285°.The focal depth profiles indicate that the seismogenic fault is nearly vertical and dips to southwest or northeast in different sections,indicating a complex geometry.There is an aftershock gap located to the southeast of the mainshock epicenter with a scale of approximately 20 km.At the eastern end of the aftershock zone,horsetaillike branch faults show the terminal effect of a large strike-slip fault.There is a NW-trending aftershock zone on the north side of the western section,which may be a branch fault triggered by the mainshock.The location of the aftershock sequence is close to the eastern section of the Kunlun Mountain Pass-Jiangcuo(KMPJ)fault.The sequence overlaps well with surface trace of the KMPJ fault.We speculate that the KMPJ fault is the main seismogenic fault of the M_(S)7.4 Maduo earthquake.
基金supported by the National Natural ScienceFoundation (Grant No. 40872076)
文摘High-quality reservoirs occur in the middle-shallow horizons of the northern Songliao Basin. The distribution and genesis of their anomalously high porosity zones were studied using measured porosities, examination of ordinary thin sections and blue epoxy resin-impregnated thin sections and by SEM. The results show that there are three anomalously high porosity zones at the depth of 450-900 m, 1,300-1,900 m, 2,050-2,350 m respectively, named zone i, zone ii and zone iii from top to bottom. Horizontally, zone i and zone ii are distributed all over the basin except in the Southeastern Uplift, while zone iii is only distributed in the Central Depression. Zone i was formed by meteoric water leaching as well as organic acid dissolution. Zones ii and iii were dominantly formed by organic acid dissolution. Additionally, clay mineral transformation generating H＋ and hydrocarbon emplacement retarding the cementation of sandstones are also important for the formation of zones ii and iii.
文摘An in situ chemical synthesis approach has been employed to prepare an Ag-chemically converted graphene (CCG) nanocomposite. The reduction of graphene oxide sheets was accompanied by generation of Ag nanoparticles. The structure and composition of the nanocomposites were confirmed by means of transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray diffraction. TEM and AFM results suggest a homogeneous distribution of Ag nanoparticles (5-10 nm in size) on CCG sheets. The intensities of the Raman signals of CCG in such nanocomposites are greatly increased by the attached silver nanoparticles, i.e., there is surface-enhanced Raman scattering activity. In addition, it was found that the antibacterial activity of free Ag nanoparticles is retained in the nanocomposites, which suggests they can be used as graphene-based biomaterials.
基金National Natural Science Foundation of China,Grant/Award Numbers:81673250,81520108021,91529305Key discipline fromthe“3-year public health promotion”programof Shanghai Municipal Health Commission。
文摘Background:The long-term trend in cancer death in a rapidly developing country provides information for cancer prophylaxis.Here,we aimed to identify the trends in cancer mortality in China during the 2004-2018 period.Methods:Using raw data from the national mortality surveillance system of China,we assessed the mortalities of all cancer and site-specific cancers during the 2004-2018 period.The participants were divided into three age groups:≥65 years,40-64 years,and≤39 years.Changing trends in cancer death by gender,residency,and tumor location were estimated using fitting joinpoint models to log-transformed crude mortality rates(CMRs)and age-standardizedmortality rates(ASMRs).Results:Cancer death accounted for 24% of all-cause of death in China during 2014-2018.The CMR of all cancer was 150.0 per 100,000 persons.Cancer was the leading cause of death in the population<65 years.The six major cancer types(lung/bronchus cancer,liver cancer,stomach cancer,esophagus cancer,colorectal cancer,and pancreas cancer)accounted for 75.85% of all cancer deaths.The CMR of all cancer increased while the ASMR decreased during 2014-2018(P<0.001).Lung/bronchus cancer and liver cancer were the leading causes of cancer death in the population<65 years,accounting for 45.31%(CMR)and 44.35%(ASMR)of all cancer death,respectively.The ASMR of liver cancer was higher in the 40-64 years population than in the≥65 years population,in contrast to the other five major cancers.The ASMRs of liver cancer,stomach cancer,and esophagus cancer decreased although they were higher in rural residents than in urban residents;the ASMRs of lung/bronchus cancer,colorectal cancer,and pancreas cancer increased in rural residents although they were higher in urban residents than in rural residents during 2014-2018.Conclusion:Although the ASMR of all cancer decreased in China during 2004-2018,lung/bronchus cancer and liver cancer remained the leading causes of cancer-related premature death.Lung/bronchus cancer,colorectal cancer,and pancreas cancer increase
基金supported by the Project of Conservation and Utilization of Agro-Wild Plants of the Ministry of Agriculture of China and Special Fund for Agro-scientific Research in the Public Interest(No.201003021)
文摘Soil salinity is one of the major abiotic stresses affecting plant growth and crop production.In the present study,salt tolerance at rice seedling stage was evaluated using 87 introgression lines（ILs）,which were derived from a cross between an elite indica cultivar Teqing and an accession of common wild rice（Oryza rufipogon Griff.）.Substantial variation was observed for four traits including salt tolerance score（STS）, relative root dry weight（RRW）,relative shoot dry weight（RSW） and relative total dry weight（RTW）.STS was significantly positively correlated with all other three traits.A total of 15 putative quantitative trait loci（QTLs） associated with these four traits were detected using single-point analysis,which were located on chromosomes 1,2,3,6,7,9 and 10 with 8%-26%explaining the phenotypic variance.The O. rufipogon-derived alleles at 13 QTLs（86.7%） could improve the salt tolerance in the Teqing background.Four QTL clusters affecting RRW, RSW and RTW were found on chromosomes 6,7,9 and 10,respectively.Among these four QTL clusters,a major cluster including three QTLs （qRRWIO,qRSWIO and qRTWIO） was found near the maker RM271 on the long arm of chromosome 10,and the O.rufipogon-derived alleles at these three loci increased RRW,RSW and RTW with additive effects of 22.7%,17.3%and 18.5%,respectively,while the phenotypic variance explained by these three individual QTLs for the three traits varied from 19%to 26%.In addition,several salt tolerant ILs were selected and could be used for identifying and utilizing favorable salt tolerant genes from common wild rice and used in the salt tolerant rice breeding program.
基金The general program of the National Natural Science Foundation of China (NSFC) under contract No.30870161
文摘A few species in the genus Grateloupia （Halymeniaceae, Rhodophyta） have been investigated in detail with respect to morphological observations and molecular analyses. In this study, the au- thors document the vegetative and reproductive structures of two new species of Grateloupia, G. dalianensis H.W.Wang et D.Zhao, sp.nov, and G. yinggehaiensis H.W.Wang et R.X.Luan, sp.nov. They both have the morphological character that carpogonial ampullae and auxiliary cell ampullae are the simple Grateloupia-type. The two species can be distinguished from other species of the genus by their distinctive morphological features respectively. Bused on ribulose-l,5-bisphosphate carboxylase/oxygenase （rbcL） gene sequences, the phylogenetic tree obtained in the study indicated that they are both embedded within the Grateloupia clade. G. dalianensis clusters a subclade with G. asiatica, and G. yinggehaiensis forms a single monophyletic subclade with G. hawaiiana.
基金support from Empa internal research grantthe SFI-SIRG award under the Agreement Number 18/SIRG/5621+2 种基金National Natural Science Foundation of China(61874166,U1832149)Natural Science Foundation of Gansu province(18JR3RA292)the Fundamental Research Funds for the Central Universities(lzujbky-2017-k21)
文摘A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well-defined structures and properties have been synthesized, and many more are theoretically predicted to exist. Due to the numerous assets including excellent mechanical properties, metallic conductivity,unique in-plane anisotropic structure, tunable band gap, and so on, MXenes rapidly positioned themselves at the forefront of the 2D materials world and have found numerous promising applications. Particular interest is devoted to applications in electrochemical energy storage, whereby 2D MXenes work either as electrodes,additives, separators, or hosts. This review summarizes recent advances in the synthesis, fundamental properties and composites of MXene and highlights the state-of-the-art electrochemical performance of MXene-based electrodes/devices.The progresses in the field of supercapacitors and Li-ion batteries, Li-S batteries, Naand other alkali metal ion batteries are reviewed, and current challenges and new opportunities for MXenes in this surging energy storage field are presented. In the focus of interest is the possibility to boost device-level performance, particularly that of rechargeable batteries, which are of utmost importance in future energy technologies. Very recently, the 2019 Nobel Prize in Chemistry was awarded to the inventors of the Li-ion battery. For sure, this will provide an additional stimulation to study fundamental aspects of electrochemical energy storage.
基金supported by the Special Fund for Agro-scientific Research in the Public Interest(201003021)the Project of Conservation and Utilization of Agricultural Wild Plants of the Ministry of Agriculture of Chinathe National High-Tech Research and Development(863)Program of China(2012AA101103)
文摘Flowering at suitable time is very important for plants to adapt to complicated environments and produce their seeds successfully for reproduction. In rice （Oryza rufipogon Griff.） photoperiod regulation is one of the important factors for controlling heading date. Common wild rice, the ancestor of cultivated rice, exhibits a late heading date and a more sensitive photoperiodic response than cultivated rice. Here, through map-based cloning, we identified a major quantitative trait loci （QTL） LHD1 （Late Heading Date 1）, an allele of DTH8/Ghd8, which controls the late heading date of wild rice and encodes a putative HAP3/NF-YB/CBF-A subunit of the CCAAT-box-binding transcription factor. Sequence analysis revealed that several variants in the coding region of LHD1 were correlated with a late heading date, and a further complementary study successfully rescued the phenotype. These results suggest that a functional site for LHD1 could be among those variants present in the coding region. We also found that LHD1 could down-regulate the expression of several floral transition activators such as Ehdl, Hd3a and RFT1 under long-day conditions, but not under short-day conditions. This indicates that LHD1 may delay flowering by repressing the expression of Ehdl, Hd3a and RFT1 under long-day conditions.
基金supported by the National Natural Science Foundation of China (No.50978003)the Beijing Natural Science Foundation (No.8091001)+1 种基金the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality (No.PHR20090502)the State Key Laboratory of Urban Water Resource and Environment (No.QAK200802)
文摘A two-stage upflow anaerobic sludge blanket （UASB） and sequencing batch reactor （SBR） system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen （TN） removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB （UASB1） to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/（m^3.day）, respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^＋-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^＋-N removal efficiency at relatively low temperature （14.9-10.9℃）. More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^＋-N once the complete nitrification and denitrification were achieved.
基金supported by the National Key Research&Development Program of China(2019YFD1002701)Agricultural Variety Improvemnt Project of Shandong Province(2019LZGC010)the Project for Extramural Scientists of the State Key Laboratory for Agrobiotech no logy(2020SKLAB6-15,2011SKLAB01-1).
文摘Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de novo assembled 816-Mb high-quality,chromosome-level haploid genome sequence for‘Zhongmu No.1’alfalfa,a heterozygous autotetraploid.The contig N50 is 3.92 Mb,and 49165 genes are annotated in the genome.The alfalfa genome is estimated to have diverged from M.truncatula approximately 8 million years ago.Genomic population analysis of 162 alfalfa accessions revealed high genetic diversity,weak population structure,and extensive gene flow from wild to cultivated alfalfa.Genome-wide association studies identified many candidate genes associated with important agronomic traits.Furthermore,we showed that MsFTa2,a Flowering Locus T homolog,whose expression is upregulated in salt-resistant germplasms,may be associated with fall dormancy and salt resistance.Taken together,these genomic resources will facilitate alfalfa genetic research and agronomic improvement.
基金Supported by Chinese Academy of Sciences (Grant No. KZCX3-SW-143)Chinese Ministry of Science and Technology (Grant No. 2002CB412602) the National Natural Science Foundation of China (Grant No. 40234049)
文摘Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in this study. The measured fission track apparent ages, combined with the simulated annealing mod- eling of the thermal history, have been used to reconstruct the thermal evolutionary histories of the samples and interpret the active history of the thrusts and faults in these areas. Thermal history mod- eling shows that earlier tectonic cooling occurred in the Garzê-Litang thrust in Miocene (~20―16 Ma) whereas the later cooling occurred mainly in the Longmen Shan thrust since ~5 Ma. Our study sug- gests that the margin of eastern Tibetan Plateau was extended by stages: through strike-slip faults deformations and related thrusts, the upper crust formed the Garzê-Litang margin in the Miocene epoch and then moved to the Longmen Shan margin since ~5 Ma. During this process, the deformations of different phases in the eastern Tibetan Plateau were absorbed by the thrusts within them and conse- quently the tectonic events of long-distance slip and extrusion up to hundreds of kilometers have not been found.
基金the National High-Tech Research Development Program of China (No. 2003AA331100).
文摘The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.
基金supported by the National Key Research and Development Program of China(2017YFA0207002)the National Natural Science Foundation of China(21577032,21607042)+1 种基金the Fundamental Research Funds for the Central Universities(2018ZD11,2018MS114,and 2016MS02)the Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection and the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘With the widespread application of radionuclide ^235U（VI）, it is inevitable that part of U（VI） is released into the natural environment. The potential toxicity and irreversibility impact on the natural environment has become one of the most forefront pollution problems in nuclear energy utilization. In this work, rod-like metal-organic framework （MOF-5） nanomaterial was synthesized by a solvothermal method and applied to efficiently adsorb U（VI） from aqueous solutions. The batch experimental results showed that the sorp- tion of U（Vl） on MOF-5 was strongly dependent on pH and independent of ionic strength, indicating that the dominant interaction mechanism was inner-sphere surface complexation and electrostatic interac- tion. The maximum sorption capacity of U（Vl） on MOF-5 was 237.0 mg]g at pH 5.0 and T = 298 K, and the sorption equilibrium reached within 5 rain. The thermodynamic parameters indicated that the removal of U（VI） on MOF-5 was a spontaneous and endothermic process. Additionally, the FT-IR and XPS analyses implied that the high sorption capacity of U（Vl） on MOF-5 was mainly attributed to the abundant oxygen-containing functional groups （i.e., C-O and C=O）. Such a facile preparation method and efficient removal performance highlighted the application of MOF-5 as a candidate for rapid and efficient radionuclide contamination＇s elimination in practical applications.
