Low iron content is a peculiar feature of marine ecosystems,where microbes have to produce iron-chelating molecules such as siderophores to survive.Very little is known about siderophore-producing bacteria in the ocea...Low iron content is a peculiar feature of marine ecosystems,where microbes have to produce iron-chelating molecules such as siderophores to survive.Very little is known about siderophore-producing bacteria in the oceans.In this study,we screened 1546 strains from marine seawater and sediments,which were deposited in the Marine Culture Collection of China(MCCC),and further analyzed the diversity of positive strains and their potential genes related to iron acquisition.Of the 1546 isolates,856 strains(55.37%)showed positive siderophore-producing activity on the Chrome Azurol Sulfonate(CAS)plates.Among these,isolates from seawater environments had a higher positive proportion(535).Some genera showed a higher proportion(>70%)of positive siderophore producers,such as Alteromonas(89/112),Marinobacter(78/109),Vibrio(21/27),Shewanella(7/8)in the Gammaproteobacteria,Sulfitobacter(17/21),Martelella(5/6)in the Alphaproteobacteria,and Joostella(6/7)in the phylum Bacteroidetes.Siderophore biosynthesis genes,including those for vanchrobactin,vibrioferrin,petrobactin,and aerobactin,as well as transport and iron storage proteins,were also identified in the positive bacterial genomes.The study revealed that a variety of bacterial strains demonstrate the production of siderophores,which could significantly contribute to the iron cycle within marine ecosystems,encompassing both seawater and marine sediments.展开更多
The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph.In this study,six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity...The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph.In this study,six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity.These strains,namely Marinobacter guineae M3B^(T),Marinobacter aromaticivorans D15-8PT,Marinobacter vulgaris F01^(T),Marinobacter profundi PWS21^(T),Marinobacter denitrificans JB02H27T,and Marinobacter sp.ST-1M(with a 99.93%similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14B^(T)),were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium.The population of cells grew in a chemolithotrophic medium,increasing from 105 cells/mL to 10^(7) cells/mL within 5 d.This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L,and occasionally produced sulfur containing complex particles.Among these Marinobacter strains,it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium.Notably,M.vulgaris F01^(T)and M.antarcticus ZS2-30^(T)showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L.Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation.Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica.The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus,which may contribute to the widespread of Marinobacter in the global ocean.展开更多
Graphene-reinforced aluminum （AI） matrix composites were successfully prepared via solution mixing and powder metallurgy in this study. The mechanical properties of the composites were studied using microhardness an...Graphene-reinforced aluminum （AI） matrix composites were successfully prepared via solution mixing and powder metallurgy in this study. The mechanical properties of the composites were studied using microhardness and tensile tests. Compared to the pure Al alloy, the graphene/Al composites showed increased strength and hardness. A tensile strength of 255 MPa was achieved for the graphene/Al com- posite with only 0.3wt% graphene, which has a 25% increase over the tensile strength of the pure Al matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to investigate the morphol- ogies, chemical compositions, and microstructures of the graphene and the graphene/A1 composites. On the basis of fractographic evidence, a relevant fracture mechanism is proposed.展开更多
Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularize...Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularized optic nerve better mimics the extracellular matrix of the embryonic porcine optic nerve and promotes the directional growth of dorsal root ganglion neurites.However,it has not been reported whether this material promotes axonal regeneration in vivo.In the present study,a porcine decellularized optic nerve was seeded with neurotrophin-3-overexpressing Schwann cells.This functional scaffold promoted the directional growth and remyelination of regenerating axons.In vitro,the porcine decellularized optic nerve contained many straight,longitudinal channels with a uniform distribution,and microscopic pores were present in the channel wall.The spatial micro topological structure and extracellular matrix were conducive to the adhesion,survival and migration of neural stem cells.The scaffold promoted the directional growth of dorsal root ganglion neurites,and showed strong potential for myelin regeneration.Furthermore,we transplanted the porcine decellularized optic nerve containing neurotrophin-3-overexpressing Schwann cells in a rat model of T10 spinal cord defect in vivo.Four weeks later,the regenerating axons grew straight,the myelin sheath in the injured/transplanted area recovered its structure,and simultaneously,the number of inflammatory cells and the expression of chondroitin sulfate proteoglycans were reduced.Together,these findings suggest that porcine decellularized optic nerve loaded with Schwann cells overexpressing neurotrophin-3 promotes the directional growth of regenerating spinal cord axons as well as myelin regeneration.All procedures involving animals were conducted in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Sun Yat-sen University(approval No.SYSU-IACUC-2019-B034)on February 28,2019.展开更多
To obtain high-quality aviation forgings of titanium alloys, b forging is an essential processing step which must be considered throughout a production process. In this work, the effect of b forging on the crystal ori...To obtain high-quality aviation forgings of titanium alloys, b forging is an essential processing step which must be considered throughout a production process. In this work, the effect of b forging on the crystal orientation and morphology of lamellar a was experimentally investigated in a two-phase titanium alloy. Strong dynamic recovery during b working resulted in the formation of low-angle grain boundary(LAGBb) inside b grains. The lamellar a can penetrate through the LAGBb, leading to similar intra a LAGBs on subgrain boundaries. Deformation banding occurs at high strain rates, and both diffusive and sharp boundaries of deformation bands can be observed.A continuous change of the b orientation in diffusive boundaries results in the formation of fine and disordered a lamellae without intra-lamellar boundary to hold the Burgers orientation relationship(OR). On sharp boundaries, it is prone to producing continuous grain boundary a(aGB) with a highly similar orientation along the boundaries. Meanwhile, there may exist several lower-angle boundaries within the grain boundary a for a smoother orientation change on the b grain boundary.展开更多
Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that t...Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that the zeolite ZSM-5 was grown on the surface of the cordieritehomogeneously. NO decomposition on the Cu exchanged ZSM-5/cordierite monolith catalysts wasalso studied. It was found that the monolith catalysts have a fine initial activity at 673K and GHSVof 10,000h-1. Such method should be a good way to make auto exhaust converter with monolithcatalyst for NOx removal.展开更多
To study deformation banding inβworking of TA15titanium alloy,hot simulation compression experiments were carried out on a Gleeble3500thermal simulator,and the microstructure was investigated by optical microscopy(OM...To study deformation banding inβworking of TA15titanium alloy,hot simulation compression experiments were carried out on a Gleeble3500thermal simulator,and the microstructure was investigated by optical microscopy(OM)and electron backscattered diffraction(EBSD).It is found that inβworking of TA15titanium alloy,deformation banding is still an important grain refinement mechanism up to temperature as high as0.7Tm(Tm is the melting temperature).Boundaries of deformation bands(DBBs)may be sharp or diffusive.Sharp DBBs retard discontinuous dynamic recrystallization(DDRX)by prohibiting nucleation,while the diffusive ones are sources of continuous dynamic recrystallization(CDRX).Deformation banding is more significant at high strain rate and large initial grain size.The average width of grain subdivisions is sensitive to strain rate but less affected by temperature and initial grain size.Multi-directional forging which produces crossing DDBs is potential to refine microstructure of small-size forgings.展开更多
Magnesium（Mg） alloy AZ31 was produced by continuous variable cross-section direct extrusion（CVCDE）to study its deformation behavior. Metallographic microscopy（OM）, transmission electron microscopy（TEM）, and sc...Magnesium（Mg） alloy AZ31 was produced by continuous variable cross-section direct extrusion（CVCDE）to study its deformation behavior. Metallographic microscopy（OM）, transmission electron microscopy（TEM）, and scanning electron microscopy（SEM） were used to observe the variations in microstructure and fracture morphology of Mg alloy AZ31 as a function of processing methods. The results reveal that grains of Mg alloy AZ31 were refined and their microstructure was homogenized by CVCDE. The recrystallization in Mg alloy AZ31 produced by CVCDE with 2 interim dies was more complete than that produced by conventional extrusion（CE） and CVCDE with 1 interim die, and the grains were finer and more uniform.Plasticity of the AZ31 alloy was improved. Fracture mode was evolved from a combination of ductility and brittleness to a sole ductile form. In summary, a CVCDE mold structure with 2 interim dies can improve microstructure, plasticity, and toughness of Mg alloy AZ31.展开更多
This paper proposes a new storage allocation rule based on target storage curves. Joint operating rules are also proposed to solve the operation problems of a multi-reservoir system with joint demands and water transf...This paper proposes a new storage allocation rule based on target storage curves. Joint operating rules are also proposed to solve the operation problems of a multi-reservoir system with joint demands and water transfer-supply projects. The joint operating rules include a water diversion rule to determine the amount of diverted water in a period, a hedging rule based on an aggregated reservoir to determine the total release from the system, and a storage allocation rule to specify the release from each reservoir. A simulation-optimization model was established to optimize the key points of the water diversion curves, the hedging rule curves, and the target storage curves using the improved particle swarm optimization （IPSO） algorithm. The multi-reservoir water supply system located in Liaoning Province, China, including a water transfer-supply project, was employed as a case study to verify the effectiveness of the proposed join operating rules and target storage curves. The results indicate that the proposed operating rules are suitable for the complex system. The storage allocation rule based on target storage curves shows an improved performance with regard to system storage distribution.展开更多
What is already known about this topic?The inclusion of meningococcal vaccines in the National Immunization Program(NIP)over several years has significantly reduced the incidence of meningococcal meningitis in China t...What is already known about this topic?The inclusion of meningococcal vaccines in the National Immunization Program(NIP)over several years has significantly reduced the incidence of meningococcal meningitis in China to historic lows.Worldwide,there has been a diversification of meningococcal serogroups,leading to a shift in dominant serogroups in China from serogroup A to serogroups C and B,accompanied by a rise in reports of serogroups Y and W.What is added by this report?An outbreak of serogroup Y Neisseria meningitidis(Nm)in a secondary vocational school involved a single confirmed severe case and 24 individuals with laboratory-confirmed Nm carriage.Epidemiological investigation revealed that the outbreak was localized to the classroom of the confirmed case.Prolonged close contact within a confined space was identified as a significant risk factor for Nm transmission.The genotype sequence identified was type 1655(ST-1655),which is categorized under clonal complex 23(CC-23)and bears resemblance to 8 previously confirmed cases of serogroup Y meningococcal meningitis within Guangdong Province.This suggests that serogroup Y infections continue to sporadically emerge and have become prevalent strains.What are the implications for public health practice?This outbreak underscores the critical need to enhance surveillance of meningococcal serogroups and population carrier,and advocate for vaccination with MenY-containing vaccines.展开更多
Background Grazing exclusion is a practical approach to restore vegetation in degraded grasslands and enhance soil organic carbon(SOC)sequestration.However,the dynamics and drivers of SOC in grasslands after grazing e...Background Grazing exclusion is a practical approach to restore vegetation in degraded grasslands and enhance soil organic carbon(SOC)sequestration.However,the dynamics and drivers of SOC in grasslands after grazing exclusion have not been well documented,especially in ecosystems with cold climates.Methods Here,we established 14 paired treatments(grazing exclusion vs.free-grazing)along a 600-km transect in the northeastern zone of the Qinghai-Tibet Plateau.After six years,we analyzed vegetation biomass dynamics and measured the soil physicochemical properties and organic C concentration across three depths(0–10,10–20,and 20–30 cm).Results Grazing exclusion signifcantly increased above-and belowground biomass(139.85%and 43.30%,respectively),pH(1.38%),total phosphorus(3.29%),nitrate nitrogen(18.03%),and ammonium nitrogen(17.81%),but signifcantly decreased soil bulk density(2.43%)and clay content(10.49%),particularly in 0–30 cm.Specifcally,SOC concentrations positively responded to grazing exclusion(0–10 cm)in 9 of the 14 sites evaluated.The efects of grazing exclusion on SOC concentrations were signifcantly higher in areas with a mean annual temperature(MAT)below 0℃compared to those in sites with a high MAT(>0℃).The SOC concentrations signifcantly correlated with the mean annual precipitation(MAP)in both treatments,but these correlations diminished with increasing soil depth.Ridge regression analysis showed that soil chemical properties(e.g.,total nitrogen and phosphorus)positively infuenced SOC accumulation,while MAT negatively infuenced it after grazing exclusion.Path analysis further revealed that MAT indirectly regulated SOC dynamics via soil chemical properties.Conclusions Our study highlights that grazing exclusion results in an asynchronous SOC and plant biomass accumulation and may be more benefcial for SOC sequestration in Qinghai-Tibet Plateau grasslands with lower temperatures.Also,humid climates promote SOC concentration in alpine grasslands.These results could help develop management practices and policies that promote sustainable grassland management.展开更多
The mechanism underlying neurogenesis during embryonic spinal cord development involves a specific ligand/receptor interaction,which may be help guide neuroengineering to boost stem cell-based neural regeneration for ...The mechanism underlying neurogenesis during embryonic spinal cord development involves a specific ligand/receptor interaction,which may be help guide neuroengineering to boost stem cell-based neural regeneration for the structural and functional repair of spinal cord injury.Herein,we hypothesized that supplying spinal cord defects with an exogenous neural network in the NT-3/fibroin-coated gelatin sponge(NF-GS)scaffold might improve tissue repair efficacy.To test this,we engineered tropomyosin receptor kinase C(TrkC)-modified neural stem cell(NSC)-derived neural network tissue with robust viability within an NF-GS scaffold.When NSCs were genetically modified to overexpress TrkC,the NT-3 receptor,a functional neuronal population dominated the neural network tissue.The pro-regenerative niche allowed the long-term survival and phenotypic maintenance of the donor neural network tissue for up to 8 weeks in the injured spinal cord.Additionally,host nerve fibers regenerated into the graft,making synaptic connections with the donor neurons.Accordingly,motor function recovery was significantly improved in rats with spinal cord injury(SCI)that received TrkC-modified NSC-derived neural network tissue transplantation.Together,the results suggested that transplantation of the neural network tissue formed in the 3D bioactive scaffold may represent a valuable approach to study and develop therapies for SCI.展开更多
The adverse effects of electronic waste （e-waste） on the human body have stirred up concern in recent years. China is one of the countries that confront serious pollution and human exposure of e-waste, and the major...The adverse effects of electronic waste （e-waste） on the human body have stirred up concern in recent years. China is one of the countries that confront serious pollution and human exposure of e-waste, and the majority of the population is exposed to potentially hazardous substances that are derived from informal e-waste recycling processes. This study reviews recent reports on human exposure to e-waste in China, with particular focus on exposure routes （e.g., inhalation and ingestion） and several toxicities of human （e.g., endocrine system, respiratory system, reproductive system, developmental toxicity, neurotoxicity, and genetic toxicity）. Pieces of evidence that associate e-waste exposure with human health effects in China are assessed. The role of toxic heavy metals （e.g., lead, cadmium, chromium, mercury, and nickel） and organic pollutants （e.g., polybrominated diphenyl ethers （PBDEs）, polychlorinated biphenyl （PCBs）, polycyclic aromatic hydrocarbons （PAHs）, polybrominated biphenyls （PBBs）, polyhalogenated aromatic hydrocarbons （PHAHs）, bisphenol A （BPA）） on human health is also briefly discussed.展开更多
Directional axon regeneration and remyelination are crucial for repair of spinal cord injury(SCI),but existing treatments do not effectively promote those processes.Here,we propose a strategy for construction of niche...Directional axon regeneration and remyelination are crucial for repair of spinal cord injury(SCI),but existing treatments do not effectively promote those processes.Here,we propose a strategy for construction of niche-specific spinal white matter-like tissue(WMLT)using decellularized optic nerve(DON)loaded with neurotrophin-3(NT-3)-overexpressing oligodendrocyte precursor cells.A rat model with a white matter defect in the dorsal spinal cord of the T10 segment was used.The WMLT transplantation group showed significant improvement in coordinated motor functions compared with the control groups.WMLT transplants integrated well with host spinal cord white matter,effectively addressing several barriers to directional axonal regeneration and myelination during SCI repair.In WMLT,laminin was found to promote development of oligodendroglial lineage(OL)cells by binding to laminin receptors.Interestingly,laminin could also guide linear axon regeneration via interactions with specific integrins on the axon surface.The WMLT developed here utilizes the unique microstructure and bioactive matrix of DON to create a niche rich in laminin,NT-3 and OL cells to achieve significant structural repair of SCI.Our protocol can help to promote research on repair of nerve injury and construction of neural tissues and organoids that form specific cell niches.展开更多
基金The National Key Research and Development Program of China under contact No.2021YFF0501304the Natural Science Foundation of Xiamen,China under contact No.3502Z20227244the Scientific Research Foundation of the Third Institute of Oceanography,MNR under contact Nos 2019021 and 2022009.
文摘Low iron content is a peculiar feature of marine ecosystems,where microbes have to produce iron-chelating molecules such as siderophores to survive.Very little is known about siderophore-producing bacteria in the oceans.In this study,we screened 1546 strains from marine seawater and sediments,which were deposited in the Marine Culture Collection of China(MCCC),and further analyzed the diversity of positive strains and their potential genes related to iron acquisition.Of the 1546 isolates,856 strains(55.37%)showed positive siderophore-producing activity on the Chrome Azurol Sulfonate(CAS)plates.Among these,isolates from seawater environments had a higher positive proportion(535).Some genera showed a higher proportion(>70%)of positive siderophore producers,such as Alteromonas(89/112),Marinobacter(78/109),Vibrio(21/27),Shewanella(7/8)in the Gammaproteobacteria,Sulfitobacter(17/21),Martelella(5/6)in the Alphaproteobacteria,and Joostella(6/7)in the phylum Bacteroidetes.Siderophore biosynthesis genes,including those for vanchrobactin,vibrioferrin,petrobactin,and aerobactin,as well as transport and iron storage proteins,were also identified in the positive bacterial genomes.The study revealed that a variety of bacterial strains demonstrate the production of siderophores,which could significantly contribute to the iron cycle within marine ecosystems,encompassing both seawater and marine sediments.
基金The National Natural Science Foundation of China under contract Nos 91951201 and 42030412the National Key R&D Program of China under contract No.2021YFF0501304the Scientific Research Foundation of Third Institute of Oceanography,MNR under contract No.2019021.
文摘The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph.In this study,six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity.These strains,namely Marinobacter guineae M3B^(T),Marinobacter aromaticivorans D15-8PT,Marinobacter vulgaris F01^(T),Marinobacter profundi PWS21^(T),Marinobacter denitrificans JB02H27T,and Marinobacter sp.ST-1M(with a 99.93%similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14B^(T)),were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium.The population of cells grew in a chemolithotrophic medium,increasing from 105 cells/mL to 10^(7) cells/mL within 5 d.This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L,and occasionally produced sulfur containing complex particles.Among these Marinobacter strains,it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium.Notably,M.vulgaris F01^(T)and M.antarcticus ZS2-30^(T)showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L.Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation.Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica.The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus,which may contribute to the widespread of Marinobacter in the global ocean.
基金financially supported by the National Natural Science Foundation of China (Nos. 51574118, 51571087, 51674292)the Natural Science Foundation of Hunan Province (No. 2015JJ4017)+1 种基金the Project of Innovation-driven Plan in Central South University (No. 2016CX007)the Hunan Provincial Science and Technology Plan Project, China (No. 2016TP1007)
文摘Graphene-reinforced aluminum （AI） matrix composites were successfully prepared via solution mixing and powder metallurgy in this study. The mechanical properties of the composites were studied using microhardness and tensile tests. Compared to the pure Al alloy, the graphene/Al composites showed increased strength and hardness. A tensile strength of 255 MPa was achieved for the graphene/Al com- posite with only 0.3wt% graphene, which has a 25% increase over the tensile strength of the pure Al matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to investigate the morphol- ogies, chemical compositions, and microstructures of the graphene and the graphene/A1 composites. On the basis of fractographic evidence, a relevant fracture mechanism is proposed.
基金supported by grants from the National Key R&D Program of China,No.2017YFA0104704(to BQL)the Young Elite Scientist Sponsorship Program(YESS)by China Association for Science and Technology(CAST),No.2018QNRC001(to BQL)+1 种基金the Fundamental Research Funds for the Central Universities,China,No.18ykpy38(to BQL)the National Natural Science Foundation of China,Nos.81971157(to BQL),81891003(to YSZ).
文摘Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury.However,achieving good outcome remains difficult.Our previous study showed that porcine decellularized optic nerve better mimics the extracellular matrix of the embryonic porcine optic nerve and promotes the directional growth of dorsal root ganglion neurites.However,it has not been reported whether this material promotes axonal regeneration in vivo.In the present study,a porcine decellularized optic nerve was seeded with neurotrophin-3-overexpressing Schwann cells.This functional scaffold promoted the directional growth and remyelination of regenerating axons.In vitro,the porcine decellularized optic nerve contained many straight,longitudinal channels with a uniform distribution,and microscopic pores were present in the channel wall.The spatial micro topological structure and extracellular matrix were conducive to the adhesion,survival and migration of neural stem cells.The scaffold promoted the directional growth of dorsal root ganglion neurites,and showed strong potential for myelin regeneration.Furthermore,we transplanted the porcine decellularized optic nerve containing neurotrophin-3-overexpressing Schwann cells in a rat model of T10 spinal cord defect in vivo.Four weeks later,the regenerating axons grew straight,the myelin sheath in the injured/transplanted area recovered its structure,and simultaneously,the number of inflammatory cells and the expression of chondroitin sulfate proteoglycans were reduced.Together,these findings suggest that porcine decellularized optic nerve loaded with Schwann cells overexpressing neurotrophin-3 promotes the directional growth of regenerating spinal cord axons as well as myelin regeneration.All procedures involving animals were conducted in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Sun Yat-sen University(approval No.SYSU-IACUC-2019-B034)on February 28,2019.
基金the support of the National Natural Science Foundation of China(No.51575449)
文摘To obtain high-quality aviation forgings of titanium alloys, b forging is an essential processing step which must be considered throughout a production process. In this work, the effect of b forging on the crystal orientation and morphology of lamellar a was experimentally investigated in a two-phase titanium alloy. Strong dynamic recovery during b working resulted in the formation of low-angle grain boundary(LAGBb) inside b grains. The lamellar a can penetrate through the LAGBb, leading to similar intra a LAGBs on subgrain boundaries. Deformation banding occurs at high strain rates, and both diffusive and sharp boundaries of deformation bands can be observed.A continuous change of the b orientation in diffusive boundaries results in the formation of fine and disordered a lamellae without intra-lamellar boundary to hold the Burgers orientation relationship(OR). On sharp boundaries, it is prone to producing continuous grain boundary a(aGB) with a highly similar orientation along the boundaries. Meanwhile, there may exist several lower-angle boundaries within the grain boundary a for a smoother orientation change on the b grain boundary.
文摘Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that the zeolite ZSM-5 was grown on the surface of the cordieritehomogeneously. NO decomposition on the Cu exchanged ZSM-5/cordierite monolith catalysts wasalso studied. It was found that the monolith catalysts have a fine initial activity at 673K and GHSVof 10,000h-1. Such method should be a good way to make auto exhaust converter with monolithcatalyst for NOx removal.
基金Projects(51205317,51575449)supported by the National Natural Science Foundation of ChinaProject(50935007)supported by the National Natural Science Foundation of China for Key Program+1 种基金Project(3102015AX004)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(104-QP-2014)supported by the Research Fund of the State Key Laboratory of Solidification Processing,China
文摘To study deformation banding inβworking of TA15titanium alloy,hot simulation compression experiments were carried out on a Gleeble3500thermal simulator,and the microstructure was investigated by optical microscopy(OM)and electron backscattered diffraction(EBSD).It is found that inβworking of TA15titanium alloy,deformation banding is still an important grain refinement mechanism up to temperature as high as0.7Tm(Tm is the melting temperature).Boundaries of deformation bands(DBBs)may be sharp or diffusive.Sharp DBBs retard discontinuous dynamic recrystallization(DDRX)by prohibiting nucleation,while the diffusive ones are sources of continuous dynamic recrystallization(CDRX).Deformation banding is more significant at high strain rate and large initial grain size.The average width of grain subdivisions is sensitive to strain rate but less affected by temperature and initial grain size.Multi-directional forging which produces crossing DDBs is potential to refine microstructure of small-size forgings.
基金financial support from the National Natural Science Foundation of China (No. 51675143)
文摘Magnesium（Mg） alloy AZ31 was produced by continuous variable cross-section direct extrusion（CVCDE）to study its deformation behavior. Metallographic microscopy（OM）, transmission electron microscopy（TEM）, and scanning electron microscopy（SEM） were used to observe the variations in microstructure and fracture morphology of Mg alloy AZ31 as a function of processing methods. The results reveal that grains of Mg alloy AZ31 were refined and their microstructure was homogenized by CVCDE. The recrystallization in Mg alloy AZ31 produced by CVCDE with 2 interim dies was more complete than that produced by conventional extrusion（CE） and CVCDE with 1 interim die, and the grains were finer and more uniform.Plasticity of the AZ31 alloy was improved. Fracture mode was evolved from a combination of ductility and brittleness to a sole ductile form. In summary, a CVCDE mold structure with 2 interim dies can improve microstructure, plasticity, and toughness of Mg alloy AZ31.
基金supported by the National Natural Science Foundation of China(Grants No.51339004 and 71171151)
文摘This paper proposes a new storage allocation rule based on target storage curves. Joint operating rules are also proposed to solve the operation problems of a multi-reservoir system with joint demands and water transfer-supply projects. The joint operating rules include a water diversion rule to determine the amount of diverted water in a period, a hedging rule based on an aggregated reservoir to determine the total release from the system, and a storage allocation rule to specify the release from each reservoir. A simulation-optimization model was established to optimize the key points of the water diversion curves, the hedging rule curves, and the target storage curves using the improved particle swarm optimization （IPSO） algorithm. The multi-reservoir water supply system located in Liaoning Province, China, including a water transfer-supply project, was employed as a case study to verify the effectiveness of the proposed join operating rules and target storage curves. The results indicate that the proposed operating rules are suitable for the complex system. The storage allocation rule based on target storage curves shows an improved performance with regard to system storage distribution.
文摘What is already known about this topic?The inclusion of meningococcal vaccines in the National Immunization Program(NIP)over several years has significantly reduced the incidence of meningococcal meningitis in China to historic lows.Worldwide,there has been a diversification of meningococcal serogroups,leading to a shift in dominant serogroups in China from serogroup A to serogroups C and B,accompanied by a rise in reports of serogroups Y and W.What is added by this report?An outbreak of serogroup Y Neisseria meningitidis(Nm)in a secondary vocational school involved a single confirmed severe case and 24 individuals with laboratory-confirmed Nm carriage.Epidemiological investigation revealed that the outbreak was localized to the classroom of the confirmed case.Prolonged close contact within a confined space was identified as a significant risk factor for Nm transmission.The genotype sequence identified was type 1655(ST-1655),which is categorized under clonal complex 23(CC-23)and bears resemblance to 8 previously confirmed cases of serogroup Y meningococcal meningitis within Guangdong Province.This suggests that serogroup Y infections continue to sporadically emerge and have become prevalent strains.What are the implications for public health practice?This outbreak underscores the critical need to enhance surveillance of meningococcal serogroups and population carrier,and advocate for vaccination with MenY-containing vaccines.
基金supported by the Second Tibetan Plateau Scientifc Expedition and Research Program(2019QZKK0405)National Natural Science Foundation of China(U23A2002,32271725)+1 种基金Collaborative Innovation Program of Hainan University(XTCX2022STB07)start-up fund of Hainan University(KYQD(ZR)21096).
文摘Background Grazing exclusion is a practical approach to restore vegetation in degraded grasslands and enhance soil organic carbon(SOC)sequestration.However,the dynamics and drivers of SOC in grasslands after grazing exclusion have not been well documented,especially in ecosystems with cold climates.Methods Here,we established 14 paired treatments(grazing exclusion vs.free-grazing)along a 600-km transect in the northeastern zone of the Qinghai-Tibet Plateau.After six years,we analyzed vegetation biomass dynamics and measured the soil physicochemical properties and organic C concentration across three depths(0–10,10–20,and 20–30 cm).Results Grazing exclusion signifcantly increased above-and belowground biomass(139.85%and 43.30%,respectively),pH(1.38%),total phosphorus(3.29%),nitrate nitrogen(18.03%),and ammonium nitrogen(17.81%),but signifcantly decreased soil bulk density(2.43%)and clay content(10.49%),particularly in 0–30 cm.Specifcally,SOC concentrations positively responded to grazing exclusion(0–10 cm)in 9 of the 14 sites evaluated.The efects of grazing exclusion on SOC concentrations were signifcantly higher in areas with a mean annual temperature(MAT)below 0℃compared to those in sites with a high MAT(>0℃).The SOC concentrations signifcantly correlated with the mean annual precipitation(MAP)in both treatments,but these correlations diminished with increasing soil depth.Ridge regression analysis showed that soil chemical properties(e.g.,total nitrogen and phosphorus)positively infuenced SOC accumulation,while MAT negatively infuenced it after grazing exclusion.Path analysis further revealed that MAT indirectly regulated SOC dynamics via soil chemical properties.Conclusions Our study highlights that grazing exclusion results in an asynchronous SOC and plant biomass accumulation and may be more benefcial for SOC sequestration in Qinghai-Tibet Plateau grasslands with lower temperatures.Also,humid climates promote SOC concentration in alpine grasslands.These results could help develop management practices and policies that promote sustainable grassland management.
基金the Chinese National Natural Science Foundation of China(81891003)the National Key R&D Program of China(2017YFA0104700)and the 111 Project for Academic Exchange Program(B13037)to Y.S.Zeng+2 种基金the Foundation of Guangdong Province(2017B020210012)to Y.S.Zeng and X.Zengthe Co-innovation Foundation of Guangzhou City(201704020221)to Y.S.Zeng,X.Zeng,and G.Lithe Start-up Foundation of Guangdong Province(Grant No.2018A030310113)to G.Li.
文摘The mechanism underlying neurogenesis during embryonic spinal cord development involves a specific ligand/receptor interaction,which may be help guide neuroengineering to boost stem cell-based neural regeneration for the structural and functional repair of spinal cord injury.Herein,we hypothesized that supplying spinal cord defects with an exogenous neural network in the NT-3/fibroin-coated gelatin sponge(NF-GS)scaffold might improve tissue repair efficacy.To test this,we engineered tropomyosin receptor kinase C(TrkC)-modified neural stem cell(NSC)-derived neural network tissue with robust viability within an NF-GS scaffold.When NSCs were genetically modified to overexpress TrkC,the NT-3 receptor,a functional neuronal population dominated the neural network tissue.The pro-regenerative niche allowed the long-term survival and phenotypic maintenance of the donor neural network tissue for up to 8 weeks in the injured spinal cord.Additionally,host nerve fibers regenerated into the graft,making synaptic connections with the donor neurons.Accordingly,motor function recovery was significantly improved in rats with spinal cord injury(SCI)that received TrkC-modified NSC-derived neural network tissue transplantation.Together,the results suggested that transplantation of the neural network tissue formed in the 3D bioactive scaffold may represent a valuable approach to study and develop therapies for SCI.
文摘The adverse effects of electronic waste （e-waste） on the human body have stirred up concern in recent years. China is one of the countries that confront serious pollution and human exposure of e-waste, and the majority of the population is exposed to potentially hazardous substances that are derived from informal e-waste recycling processes. This study reviews recent reports on human exposure to e-waste in China, with particular focus on exposure routes （e.g., inhalation and ingestion） and several toxicities of human （e.g., endocrine system, respiratory system, reproductive system, developmental toxicity, neurotoxicity, and genetic toxicity）. Pieces of evidence that associate e-waste exposure with human health effects in China are assessed. The role of toxic heavy metals （e.g., lead, cadmium, chromium, mercury, and nickel） and organic pollutants （e.g., polybrominated diphenyl ethers （PBDEs）, polychlorinated biphenyl （PCBs）, polycyclic aromatic hydrocarbons （PAHs）, polybrominated biphenyls （PBBs）, polyhalogenated aromatic hydrocarbons （PHAHs）, bisphenol A （BPA）） on human health is also briefly discussed.
基金supported by grants from the National Natural Science Foundation of China,Nos.81891003(to YSZ),81971157(to BQL)the National Key R&D Program of China,Nos.2017YFA0104704(to BQL),2017YFA0104701(to YSZ)+5 种基金the Young Elite Scientist Sponsorship Program by CAST(YESS),No.2018QNRC001(to BQL)the Fundamental Research Funds for the Central Universities,China,Nos.20ykpy156(to YHM)the 111 Project for Academic Exchange Program,China,No.B13037(to YSZ,YD and YHM)the Natural Science Foundation of Guangdong Province,China,Nos.2018A030310110(to YHM),2020A1515011537(to YHM)the Foundation of Guangdong Province,China,No.2017B020210012(to YSZ and XZ)the Start-up Foundation of Guangdong Province,China,No.2018A030310113(to GL).
文摘Directional axon regeneration and remyelination are crucial for repair of spinal cord injury(SCI),but existing treatments do not effectively promote those processes.Here,we propose a strategy for construction of niche-specific spinal white matter-like tissue(WMLT)using decellularized optic nerve(DON)loaded with neurotrophin-3(NT-3)-overexpressing oligodendrocyte precursor cells.A rat model with a white matter defect in the dorsal spinal cord of the T10 segment was used.The WMLT transplantation group showed significant improvement in coordinated motor functions compared with the control groups.WMLT transplants integrated well with host spinal cord white matter,effectively addressing several barriers to directional axonal regeneration and myelination during SCI repair.In WMLT,laminin was found to promote development of oligodendroglial lineage(OL)cells by binding to laminin receptors.Interestingly,laminin could also guide linear axon regeneration via interactions with specific integrins on the axon surface.The WMLT developed here utilizes the unique microstructure and bioactive matrix of DON to create a niche rich in laminin,NT-3 and OL cells to achieve significant structural repair of SCI.Our protocol can help to promote research on repair of nerve injury and construction of neural tissues and organoids that form specific cell niches.
