The heterogeneous magnesium(Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanic...The heterogeneous magnesium(Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially,the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.展开更多
Biomass activated carbon(BAC)was produced from ginger stems by carbonization and activation presented high specific surface areas and mesoporous structures.The carbonization temperature of the ginger stems were contro...Biomass activated carbon(BAC)was produced from ginger stems by carbonization and activation presented high specific surface areas and mesoporous structures.The carbonization temperature of the ginger stems were controlled within 500~900℃.The optimal carbonization condition is as follows:carbonization temperature of 700℃,carbonization time of 6 h.The determined optimum activation condition is:temperature of 800℃,activator of KOH and carbonized product/alkali ratio of 1:4(w/w).The carbonization yield,BAC yield and Brunauer-Emmett-Teller(BET)surface area were measured and the adsorption performance of BAC to nitrogen was investigated.The results showed that the nitrogen adsorption isotherm curve was as type I isotherm.It was finally determined that the BET surface area was 660 m2/g under the abovementioned optimal conditions of carbonization and activation.The FESEM analysis indicates that the obtained BAC is of micropore structure.展开更多
Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation pro...Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation process.Under time and resource constraints,we applied a more convenient approach.We investigated two MtGA3ox genes,MtGA3ox1 and MtGA3ox2,of Medicago truncatula,a diploid legume model species,finding that MtGA3ox1 plays a major role in GA-regulated plant architecture.Mutation of neither gene affected nitrogenase activity.These results suggest that MtGA3ox1 can be used in semidwarf and prostrate alfalfa breeding.Based on the M.truncatula MtGA3ox1 sequence,MsGA3ox1 was cloned from alfalfa,and two knockout targets were designed.An efficient CRISPR/Cas9-based genome editing protocol was used to generate msga3ox1 mutants in alfalfa.We obtained three lines that carried mutations in all four alleles in the T0 generation.Fifteen clonal plants were vegetatively propagated from each transgenic line using shoot cuttings.The plant height and internode length of msga3ox1 null mutants were significantly decreased.The number of total lateral branches,leaf/stem ratio and crude protein content of aerial plant parts of msga3ox1 mutants were significantly increased.Thus,we obtained semi-dwarf and prostrate alfalfa by gene editing.展开更多
Fucosyltransferase 8(Fut8)and core fucosylation play critical roles in regulating various biological processes,including immune response,signal transduction,proteasomal degradation,and energy metabolism.However,the fu...Fucosyltransferase 8(Fut8)and core fucosylation play critical roles in regulating various biological processes,including immune response,signal transduction,proteasomal degradation,and energy metabolism.However,the function and underlying mechanism of Fut8 and core fucosylation in regulating adult neurogenesis remains unknown.We have shown that Fut8 and core fucosylation display dynamic features during the differentiation of adult neural stem/progenitor cells(aNSPCs)and postnatal brain development.Fut8 depletion reduces the proliferation of a NSPCs and inhibits neuronal differentiation of aNSPCs in vitro and in vivo,respectively.Additionally,Fut8 deficiency impairs learning and memory in mice.Mechanistically,Fut8 directly interacts with integrinα6(Itga6),an upstream regulator of the PI3kAkt signaling pathway,and catalyzes core fucosylation of Itga6.Deletion of Fut8 enhances the ubiquitination of Itga6 by promoting the binding of ubiquitin ligase Trim21 to Itga6.Low levels of Itga6 inhibit the activity of the PI3K/Akt signaling pathway.Moreover,the Akt agonist SC79 can rescue neurogenic and behavioral deficits caused by Fut8 deficiency.In summary,our study uncovers an essential function of Fut8 and core fucosylation in regulating adult neurogenesis and sheds light on the underlying mechanisms.展开更多
For the first time,the flash sintering(FS)of high-purity alumina at room temperature,which was previously considered unachievable due to its low electrical conductivity,was conducted herein.The electrical arc originat...For the first time,the flash sintering(FS)of high-purity alumina at room temperature,which was previously considered unachievable due to its low electrical conductivity,was conducted herein.The electrical arc originating from surface flashover was harnessed to induce FS at room temperature and low air pressure.The successful FS of high-purity alumina was realized at 60 kPa under the arc constraint,resulting in a notable relative density of the alumina sample of 98.7%.The electric–thermal coupling between the arc and high-purity alumina sample during the arc-induced FS process was analyzed via the finite element simulation method.The results revealed the thermal and electrical effects of the arc on the sample,which ultimately enhance the electrical conductivity of the alumina sample.The formation of a conductive channel on the sample surface,a result of increased electrical conductivity,was the pivotal factor in achieving FS in high-purity alumina at room temperature.The arc constraint technique can be applied to numerous materials,such as ionic conductors,semiconductors,and even insulators,under room-temperature and low-air-pressure conditions.展开更多
Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide. The rice-M, oryzae pathosystem has become a model in the study of plant-fungal interactions beca...Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide. The rice-M, oryzae pathosystem has become a model in the study of plant-fungal interactions because of its scientific advancement and economic importance. Recent studies have identified a number of new pathogen- associated molecular patterns (PAMPs) and effectors from the blast fungus that trigger rice immune responses upon perception. Interaction analyses between avirulence effectors and their cognate resistance proteins have provided new insights into the molecular basis of plant-fungal interactions. In this review, we summarize the recent research on the characterization of those genes in both M. oryzae and rice that are important for the PAMP- and effector-triggered immunity recognition and signaling processes. We also discuss future directions for research that will further our understanding of this pathosystem.展开更多
A study on phytoliths and their climate indexes is carried out from Homo erectus?cave deposits in HuluCave, Nanjing. Evidence shows that phytolith assemblages of the cave deposits are dominated by the cold resistant t...A study on phytoliths and their climate indexes is carried out from Homo erectus?cave deposits in HuluCave, Nanjing. Evidence shows that phytolith assemblages of the cave deposits are dominated by the cold resistant types with a lower warm index, reflecting an overall cold inclined climate. This possibly connects the cave deposits with glacial climate to a great extent, which is in accordance with thenorthern fauna revealed by fossil mammals and temperateclimate indicated by pollen assemblages. According to the distributional state of the phytoliths and their climate in-dexes on 4 profiles in the cave, it is revealed that profiles Ⅰand Ⅱ display certain cold/warm, and dry/wet fluctuations; profile Ⅲ shows a humid and cold condition with the high-est humility in the cave deposits; while profile Ⅳ indicates a possible quick accumulating process because of its stableclimate indexes except for its bottom and top.展开更多
Estuaries are important sites for mercury (Hg) methylation, with sulfate-reducing bacteria (SRB) thought to be the main Hg methylators. Distributions of total mercury (THg) and methylmercury (MeHg) in mangrove...Estuaries are important sites for mercury (Hg) methylation, with sulfate-reducing bacteria (SRB) thought to be the main Hg methylators. Distributions of total mercury (THg) and methylmercury (MeHg) in mangrove sediment and sediment core from Jiulong River Estuary Provincial Mangrove Reserve, China were determined and the possible mechanisms of Hg methylation and their controlling factors in mangrove sediments were investigated. Microbiological and geochemical parameters were also determined. Results showed that SRB constitute a small fraction of total bacteria (TB) in both surface sediments and the profile of sediments. The content of THg, MeHg, TB, and SRB were (350 ± 150) ng/g, (0.47 ± 0.11) ng/g, (1.4× 10^011 ± 4.1 × 10^9) cfu/g dry weight (dw), and (5.0× 10^6 d: 2.7 × 10^6) cfu/g dw in surficial sediments, respectively, and (240 ± 24) ng/g, (0.30 ± 0.15) ng/g, (1.9 × 10^11 ± 4.2 × 10^9) cfu/g dw, and (1.3 × 10^6 ± 2.0 × 10^6) cfu/g dw in sediment core, respectively. Results showed that THg, MeHg, TB, MeHg/THg, salinity and total sulfur (TS) increased with depth, but total organic matter (TOM), SRB, and pH decreased with depth. Concentrations of MeHg in sediments showed significant positive correlation with THg, salinity, TS, and MeHg/THg, and significant negative correlation with SRB, TOM, and pH. It was concluded that other microbes, rather than SRB, may also act as main Hg methylators in mangrove sediments.展开更多
The effect of the applied electric field on the conductive behavior of zirconia ceramics is studied by measuring its initial current-voltage curve at various temperatures. The results show that when the field strength...The effect of the applied electric field on the conductive behavior of zirconia ceramics is studied by measuring its initial current-voltage curve at various temperatures. The results show that when the field strength is higher than the threshold for flash-sintering, the curves exhibit a nonlinear behavior by having an additional current on top of the linear current according to Ohm's law. Analyzing its transport behavior reveals that the additional current density is due to the extra oxygen vacancies induced by the electric field. The formation rate of the extra vacancies and associated current was related to the field strength.展开更多
Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains...Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation(LLPS)when facing DNA double-strand breaks(DSBs).The histone methyltransferase SUVR2(MtSUVR2)has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation(H3K9me1)to H3K9me2/3 in vitro and in Medicago truncatula.Under DNA damage,the proportion of heterochromatin decreased and the level of DSB damage marker y-H2AX increased in suvr2 mutants,indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage.Interestingly,MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites,and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments.The IDR1 and lowcomplexity domain regions of MtSUVR2 determined its phase separation in the nucleus,whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51.Furthermore,we found that MtSUVR2 drove the phase separation of MtRAD51 to form"DNA repair bodies,"which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells.Taken together,our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.展开更多
Increasing nanoparticle volume fraction has been proved to be effective in improving the strength of nanoparticle reinforced Al matrix nanocomposite. However, the underlying mechanisms for the ultrahigh strength of th...Increasing nanoparticle volume fraction has been proved to be effective in improving the strength of nanoparticle reinforced Al matrix nanocomposite. However, the underlying mechanisms for the ultrahigh strength of those nanocomposites with high volume fraction(> 10 vol.%) nanoparticles are short of experimental research. In this study, the strengthening mechanisms of high strength Al matrix nanocomposite reinforced with 15 vol.% Al_(2)O_(3) nanoparticles were investigated experimentally and analyzed theoretically. The results show that the thermal mismatch induced geometrically necessary dislocations exhibit a negligible strengthening effect, because of their low density in the nanocomposite that is contradiction to the conventional dislocation punch model. Orowan mechanism makes a major strengthening contribution in view of the deformation process dominated by nanoparticle-dislocation interactions due to the extreme pinning effect of nanoparticles on dislocation motion. In addition, the several mechanisms including grain boundary strengthening, load transfer strengthening, and elastic modulus mismatch induced dislocation strengthening contribute to the strength increase.展开更多
In this study, magnesium matrix composites reinforced with different loading of AlN particles were fabricated by the powder metallurgy technique. The microstructure, bending strength and fracture behavior of the resul...In this study, magnesium matrix composites reinforced with different loading of AlN particles were fabricated by the powder metallurgy technique. The microstructure, bending strength and fracture behavior of the resulting Mg-Al/Al N composites were investigated. It showed that the 5 wt% AlN reinforcements led to the highest densification and bending strength. The total strengthening effect of AlN particles was predicted by considering the contributions of CTE mismatch between the matrix and the particles,load bearing and Hall-Petch mechanism. The results revealed that the increase of dislocation density,the change of Mg17Al12 phase morphology, and the effective load transfer were the major strengthening contributors to the composites. The fracture of the composites altered from plastic to brittle mode with increasing reinforcement content. The regions of clustered particles in the composites were easy to be damaged under external load, and the fracture occurred mainly along grain boundaries.展开更多
The nanostructured Al-based composites possess the combination of high yield strength and good ductility. In this paper, a micromechanical model is presented to simulate the mechanical response of bimodal nanostructur...The nanostructured Al-based composites possess the combination of high yield strength and good ductility. In this paper, a micromechanical model is presented to simulate the mechanical response of bimodal nanostructured A1 and the particle-reinforced aluminum matrix composite (PAMC). The constitutive relations for different phases are addressed in the model, as well as the contribution of microcracks. Numerical results show that the model can successfully describe the enhanced strength and ductility of the bimodal nanostructured AI, and the predictions of the PAMC are in good agreement with the experimental data. It is worth noting that the strength and ductility are sensitive to the volume fraction of constituents and the distribution of rnicrocracks in both bimodal nanostructured A1 and PAMG. Therefore, the present theoretical results can be used to optimize the microstructure for improving the mechanical properties of nanostructured Al-based composites.展开更多
The complex metallic alloy(CMA), Al(76.8)Fe(24), was in-situ synthesized in the Al-based hybrid composite by powder metallurgy technique. The structural analysis by X-ray diffraction, scanning electron microscop...The complex metallic alloy(CMA), Al(76.8)Fe(24), was in-situ synthesized in the Al-based hybrid composite by powder metallurgy technique. The structural analysis by X-ray diffraction, scanning electron microscopy,and transmission electron microscopy indicated that the Al(76.8)Fe(24) CMA phase was formed by diffusion of Fe atoms into the Al matrix during the sintering stage. The formation of the CMA phase was mainly determined by the sintering temperature which was just above the eutectic temperature of Al–Fe. Moreover,the fully dense Al-based hybrid composite was obtained and exhibited ultrahigh strength ~1100 MPa,indicating that this method is expected to be effective in producing CMA particle reinforced Al-based hybrid composite.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 51871187)Department of Science and Technology of Sichuan Province (Grant No. 2020YFG0140)Fundamental Research Funds for the Central Universities (Grant No. 2682019LK04)。
文摘The heterogeneous magnesium(Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially,the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.
基金financially supported by the Natural Science Foundation of Shandong Province (ZR2017QB002)the key scientific research projects in Shandong Province (2018GGX104003)+2 种基金the Taishan Scholar Program of Shandong (ts201511033)the Foundation of Key Laboratory of Pulp and Paper Science and Technology of Ministry of Education/ Shandong Province of China(No.KF201705)Shandong Province major innovation project (2018CXGC1001)
文摘Biomass activated carbon(BAC)was produced from ginger stems by carbonization and activation presented high specific surface areas and mesoporous structures.The carbonization temperature of the ginger stems were controlled within 500~900℃.The optimal carbonization condition is as follows:carbonization temperature of 700℃,carbonization time of 6 h.The determined optimum activation condition is:temperature of 800℃,activator of KOH and carbonized product/alkali ratio of 1:4(w/w).The carbonization yield,BAC yield and Brunauer-Emmett-Teller(BET)surface area were measured and the adsorption performance of BAC to nitrogen was investigated.The results showed that the nitrogen adsorption isotherm curve was as type I isotherm.It was finally determined that the BET surface area was 660 m2/g under the abovementioned optimal conditions of carbonization and activation.The FESEM analysis indicates that the obtained BAC is of micropore structure.
基金supported by the Agricultural Variety Improvement Project of Shandong Province(2019LZGC010)the National Key Research and Development Program of China(2019YFD1002701).
文摘Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation process.Under time and resource constraints,we applied a more convenient approach.We investigated two MtGA3ox genes,MtGA3ox1 and MtGA3ox2,of Medicago truncatula,a diploid legume model species,finding that MtGA3ox1 plays a major role in GA-regulated plant architecture.Mutation of neither gene affected nitrogenase activity.These results suggest that MtGA3ox1 can be used in semidwarf and prostrate alfalfa breeding.Based on the M.truncatula MtGA3ox1 sequence,MsGA3ox1 was cloned from alfalfa,and two knockout targets were designed.An efficient CRISPR/Cas9-based genome editing protocol was used to generate msga3ox1 mutants in alfalfa.We obtained three lines that carried mutations in all four alleles in the T0 generation.Fifteen clonal plants were vegetatively propagated from each transgenic line using shoot cuttings.The plant height and internode length of msga3ox1 null mutants were significantly decreased.The number of total lateral branches,leaf/stem ratio and crude protein content of aerial plant parts of msga3ox1 mutants were significantly increased.Thus,we obtained semi-dwarf and prostrate alfalfa by gene editing.
基金supported in part by the National Natural Science Foundation of China(92049108,82371182)Central Guiding Fund for Local Science and Technology Development Projects(2023ZY1058)the National Key Research and Development Program of China(2017YFE0196600)。
文摘Fucosyltransferase 8(Fut8)and core fucosylation play critical roles in regulating various biological processes,including immune response,signal transduction,proteasomal degradation,and energy metabolism.However,the function and underlying mechanism of Fut8 and core fucosylation in regulating adult neurogenesis remains unknown.We have shown that Fut8 and core fucosylation display dynamic features during the differentiation of adult neural stem/progenitor cells(aNSPCs)and postnatal brain development.Fut8 depletion reduces the proliferation of a NSPCs and inhibits neuronal differentiation of aNSPCs in vitro and in vivo,respectively.Additionally,Fut8 deficiency impairs learning and memory in mice.Mechanistically,Fut8 directly interacts with integrinα6(Itga6),an upstream regulator of the PI3kAkt signaling pathway,and catalyzes core fucosylation of Itga6.Deletion of Fut8 enhances the ubiquitination of Itga6 by promoting the binding of ubiquitin ligase Trim21 to Itga6.Low levels of Itga6 inhibit the activity of the PI3K/Akt signaling pathway.Moreover,the Akt agonist SC79 can rescue neurogenic and behavioral deficits caused by Fut8 deficiency.In summary,our study uncovers an essential function of Fut8 and core fucosylation in regulating adult neurogenesis and sheds light on the underlying mechanisms.
基金This work was supported by the National Natural Science Foundation of China(52077118)Guangdong Basic and Applied Basic Research Foundation(2021A1515011778)Key Laboratory of Engineering Dielectrics and Its Application(Harbin University of Science and Technology),Ministry of Education(KFM202204).
文摘For the first time,the flash sintering(FS)of high-purity alumina at room temperature,which was previously considered unachievable due to its low electrical conductivity,was conducted herein.The electrical arc originating from surface flashover was harnessed to induce FS at room temperature and low air pressure.The successful FS of high-purity alumina was realized at 60 kPa under the arc constraint,resulting in a notable relative density of the alumina sample of 98.7%.The electric–thermal coupling between the arc and high-purity alumina sample during the arc-induced FS process was analyzed via the finite element simulation method.The results revealed the thermal and electrical effects of the arc on the sample,which ultimately enhance the electrical conductivity of the alumina sample.The formation of a conductive channel on the sample surface,a result of increased electrical conductivity,was the pivotal factor in achieving FS in high-purity alumina at room temperature.The arc constraint technique can be applied to numerous materials,such as ionic conductors,semiconductors,and even insulators,under room-temperature and low-air-pressure conditions.
基金This work was supported by the US NSF-IOS to G.L.W. (1120949)the National Natural Science Foundation of China to W.D.L. (31272034)+3 种基金 Y.S.N. (31101405) and X.L.W. (31101404) the 973 Project (2012CBl14005) of Ministry of Science and Technology China and the National Transgenic Crop Initiative to G.L.W. (2012ZX08009001) and the Scientific and Technological Innovation Program of Hunan Universities from Hunan Department of Science and Technology and the Program for Innovative Research Team in University from Ministry of Education in China IRT1239) to Z.L.W. No conflict of interest declared.
文摘Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide. The rice-M, oryzae pathosystem has become a model in the study of plant-fungal interactions because of its scientific advancement and economic importance. Recent studies have identified a number of new pathogen- associated molecular patterns (PAMPs) and effectors from the blast fungus that trigger rice immune responses upon perception. Interaction analyses between avirulence effectors and their cognate resistance proteins have provided new insights into the molecular basis of plant-fungal interactions. In this review, we summarize the recent research on the characterization of those genes in both M. oryzae and rice that are important for the PAMP- and effector-triggered immunity recognition and signaling processes. We also discuss future directions for research that will further our understanding of this pathosystem.
文摘A study on phytoliths and their climate indexes is carried out from Homo erectus?cave deposits in HuluCave, Nanjing. Evidence shows that phytolith assemblages of the cave deposits are dominated by the cold resistant types with a lower warm index, reflecting an overall cold inclined climate. This possibly connects the cave deposits with glacial climate to a great extent, which is in accordance with thenorthern fauna revealed by fossil mammals and temperateclimate indicated by pollen assemblages. According to the distributional state of the phytoliths and their climate in-dexes on 4 profiles in the cave, it is revealed that profiles Ⅰand Ⅱ display certain cold/warm, and dry/wet fluctuations; profile Ⅲ shows a humid and cold condition with the high-est humility in the cave deposits; while profile Ⅳ indicates a possible quick accumulating process because of its stableclimate indexes except for its bottom and top.
基金supported by the National Natural Science Foundation of China (No.40676064,30530150)the Guangdong-HK Technology Cooperation Funding Scheme (No.08-Lh-04)+1 种基金the Key Laboratory of Nuclear Resources and Environment (East China Institute of Technology), the Ministry of Education (No.070717,081203)the State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry, Chinese Academy of Sciences,and the National Supporting Projects of Science & Technology in Forestry (2009BADB2B0605)
文摘Estuaries are important sites for mercury (Hg) methylation, with sulfate-reducing bacteria (SRB) thought to be the main Hg methylators. Distributions of total mercury (THg) and methylmercury (MeHg) in mangrove sediment and sediment core from Jiulong River Estuary Provincial Mangrove Reserve, China were determined and the possible mechanisms of Hg methylation and their controlling factors in mangrove sediments were investigated. Microbiological and geochemical parameters were also determined. Results showed that SRB constitute a small fraction of total bacteria (TB) in both surface sediments and the profile of sediments. The content of THg, MeHg, TB, and SRB were (350 ± 150) ng/g, (0.47 ± 0.11) ng/g, (1.4× 10^011 ± 4.1 × 10^9) cfu/g dry weight (dw), and (5.0× 10^6 d: 2.7 × 10^6) cfu/g dw in surficial sediments, respectively, and (240 ± 24) ng/g, (0.30 ± 0.15) ng/g, (1.9 × 10^11 ± 4.2 × 10^9) cfu/g dw, and (1.3 × 10^6 ± 2.0 × 10^6) cfu/g dw in sediment core, respectively. Results showed that THg, MeHg, TB, MeHg/THg, salinity and total sulfur (TS) increased with depth, but total organic matter (TOM), SRB, and pH decreased with depth. Concentrations of MeHg in sediments showed significant positive correlation with THg, salinity, TS, and MeHg/THg, and significant negative correlation with SRB, TOM, and pH. It was concluded that other microbes, rather than SRB, may also act as main Hg methylators in mangrove sediments.
基金financially supported by National Natural Science Foundation of China(Grant Nos.51372202,51402237,51532003,51602264)State Key Laboratory of Traction Power(Grand No.2015TPL Z01)
文摘The effect of the applied electric field on the conductive behavior of zirconia ceramics is studied by measuring its initial current-voltage curve at various temperatures. The results show that when the field strength is higher than the threshold for flash-sintering, the curves exhibit a nonlinear behavior by having an additional current on top of the linear current according to Ohm's law. Analyzing its transport behavior reveals that the additional current density is due to the extra oxygen vacancies induced by the electric field. The formation rate of the extra vacancies and associated current was related to the field strength.
基金the Key Projects in Science and Technology of Inner Mongolia(2021ZD0031)the Opening Fund of the Key Laboratory of Forage and Endemic Crop Biology,the Ministry of Education(FECBOF2021001)+1 种基金the National Natural Science Foundation of China(NFSC32070272)for supporting this work.
文摘Maintaining genomic integrity and stability is particularly important for stem cells,which are at the top of the cell lineage origin.Here,we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation(LLPS)when facing DNA double-strand breaks(DSBs).The histone methyltransferase SUVR2(MtSUVR2)has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation(H3K9me1)to H3K9me2/3 in vitro and in Medicago truncatula.Under DNA damage,the proportion of heterochromatin decreased and the level of DSB damage marker y-H2AX increased in suvr2 mutants,indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage.Interestingly,MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites,and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments.The IDR1 and lowcomplexity domain regions of MtSUVR2 determined its phase separation in the nucleus,whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51.Furthermore,we found that MtSUVR2 drove the phase separation of MtRAD51 to form"DNA repair bodies,"which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells.Taken together,our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.
基金financially supported by the Key Research and Development Project in Sichuan Province(Grant No.2020YFG0140)the Fundamental Research Funds for the Central Universities(Grant No.2682020CX47)+1 种基金the China Postdoctoral Science Foundation(Grant No.2020M683349)。
文摘Increasing nanoparticle volume fraction has been proved to be effective in improving the strength of nanoparticle reinforced Al matrix nanocomposite. However, the underlying mechanisms for the ultrahigh strength of those nanocomposites with high volume fraction(> 10 vol.%) nanoparticles are short of experimental research. In this study, the strengthening mechanisms of high strength Al matrix nanocomposite reinforced with 15 vol.% Al_(2)O_(3) nanoparticles were investigated experimentally and analyzed theoretically. The results show that the thermal mismatch induced geometrically necessary dislocations exhibit a negligible strengthening effect, because of their low density in the nanocomposite that is contradiction to the conventional dislocation punch model. Orowan mechanism makes a major strengthening contribution in view of the deformation process dominated by nanoparticle-dislocation interactions due to the extreme pinning effect of nanoparticles on dislocation motion. In addition, the several mechanisms including grain boundary strengthening, load transfer strengthening, and elastic modulus mismatch induced dislocation strengthening contribute to the strength increase.
基金financially supported by the State Key Laboratory for Mechanical Behavior of Materials (No. 20151712)
文摘In this study, magnesium matrix composites reinforced with different loading of AlN particles were fabricated by the powder metallurgy technique. The microstructure, bending strength and fracture behavior of the resulting Mg-Al/Al N composites were investigated. It showed that the 5 wt% AlN reinforcements led to the highest densification and bending strength. The total strengthening effect of AlN particles was predicted by considering the contributions of CTE mismatch between the matrix and the particles,load bearing and Hall-Petch mechanism. The results revealed that the increase of dislocation density,the change of Mg17Al12 phase morphology, and the effective load transfer were the major strengthening contributors to the composites. The fracture of the composites altered from plastic to brittle mode with increasing reinforcement content. The regions of clustered particles in the composites were easy to be damaged under external load, and the fracture occurred mainly along grain boundaries.
基金financially supported by State Key Laboratory of Traction Power (Grant No.2015TPL_Z01)Fundamental Research Funds for the Central Universities (Grant No.2682015RC07)+1 种基金support received from the National Natural Science Foundation of China (Grant Nos.11472243,and 11621062)Doctoral Fund of Ministry of Education of China (20130101120175)
文摘The nanostructured Al-based composites possess the combination of high yield strength and good ductility. In this paper, a micromechanical model is presented to simulate the mechanical response of bimodal nanostructured A1 and the particle-reinforced aluminum matrix composite (PAMC). The constitutive relations for different phases are addressed in the model, as well as the contribution of microcracks. Numerical results show that the model can successfully describe the enhanced strength and ductility of the bimodal nanostructured AI, and the predictions of the PAMC are in good agreement with the experimental data. It is worth noting that the strength and ductility are sensitive to the volume fraction of constituents and the distribution of rnicrocracks in both bimodal nanostructured A1 and PAMG. Therefore, the present theoretical results can be used to optimize the microstructure for improving the mechanical properties of nanostructured Al-based composites.
基金the financial support from the State Key Laboratory of Traction Power (Grant No. 2015TPL Z01)the State Key Laboratory of Solidification Processing (Grant Nos. 82TZ-2013 and SKLSP201609)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2682015RC07)the “111” Project (Grant No. B08040)
文摘The complex metallic alloy(CMA), Al(76.8)Fe(24), was in-situ synthesized in the Al-based hybrid composite by powder metallurgy technique. The structural analysis by X-ray diffraction, scanning electron microscopy,and transmission electron microscopy indicated that the Al(76.8)Fe(24) CMA phase was formed by diffusion of Fe atoms into the Al matrix during the sintering stage. The formation of the CMA phase was mainly determined by the sintering temperature which was just above the eutectic temperature of Al–Fe. Moreover,the fully dense Al-based hybrid composite was obtained and exhibited ultrahigh strength ~1100 MPa,indicating that this method is expected to be effective in producing CMA particle reinforced Al-based hybrid composite.