Droplet coalescence in liquid steel was carefully investigated through observations of the distribution pattern of inclusions in solidified steel samples. The process of droplet coalescence was slow, and the critical ...Droplet coalescence in liquid steel was carefully investigated through observations of the distribution pattern of inclusions in solidified steel samples. The process of droplet coalescence was slow, and the critical Weber number(We) was used to evaluate the coalescence or separation of droplets. The relationship between the collision parameter and the critical We indicated whether slow coalescence or bouncing of droplets occurred. The critical We was 5.5, which means that the droplets gradually coalesce when We ≤ 5.5, whereas they bounce when We > 5.5. For the carbonate wire feeding into liquid steel, a mathematical model implementing a combined computational fluid dynamics(CFD)–discrete element method(DEM) approach was developed to simulate the movement and coalescence of variably sized droplets in a bottom-argon-blowing ladle. In the CFD model, the flow field was solved on the premise that the fluid was a continuous medium. Meanwhile, the droplets were dispersed in the DEM model, and the coalescence criterion of the particles was added to simulate the collision-coalescence process of the particles. The numerical simulation results and observations of inclusion coalescence in steel samples are consistent.展开更多
Electrocatalytic carb on dioxide reducti on(CO_(2)R)presents a promising route to establish zero-e mission carb on cycle and store in termittent ren ewable energy into chemical fuels for steady energy supply.Methanol ...Electrocatalytic carb on dioxide reducti on(CO_(2)R)presents a promising route to establish zero-e mission carb on cycle and store in termittent ren ewable energy into chemical fuels for steady energy supply.Methanol is an ideal energy carrier as alternative fuels and one of the most important commodity chemicals.Nevertheless,methanol is currently mainly produced from fossil-based syngas,the production of which yields tremendous carb on emission globally.Direct CO_(2)R towards metha nol poses great potential to shift the paradigm of methanol production.In this perspective,we focus our discussions on producing methanol from electrochemical CO_(2)R,using metallomacrocyclic molecules as the model catalysts.We discuss the motivation of having methanol as the sole CO_(2)R product,the documented application of metallomacrocyclic catalysts for CO_(2)R,and recent advance in catalyzing CO_(2) to methanol with cobalt phthalocyanine-based catalysts.We attempt to understand the key factors in determining the activity,selectivity,and stability of electrocatalytic CO_(2)-to-methanol conversion,and to draw mechanistic insights from existing observations.Finally,we identify the challenges hindering methanol electrosynthesis directly from CO_(2) and some intriguing directions worthy of further investigation and exploration.展开更多
A previous functional magnetic resonance imaging study reported evidence for parallel memory traces in the hippocampus: a controlled match signal detecting matches to internally-generated goal states and an automatic...A previous functional magnetic resonance imaging study reported evidence for parallel memory traces in the hippocampus: a controlled match signal detecting matches to internally-generated goal states and an automatic mismatch signal identifying unpredicted perceptual novelty. However, the timing information in this process is unknown. In the current study, facilitated by the high spatial and temporal resolution of intracranial recording from human patients, we confirmed that the left posterior hippocampus played an important role in the goal match enhancement effect, in which combinations of object identity and location were involved. We also found that this effect happened within 520 ms to 735 ms after the probe onset, *150 ms later than the perceptual mismatch enhancement found bilaterally in both the anterior and posterior hippocampus. More specifically, the latency of the perceptual mismatch enhancement effect of the right hippocampus was positively correlated with the performance accuracy. These results suggested that the hippocampus is crucial in working memory if features binding with location are involved in the task and the goal match enhancement effect happens after perceptual mismatch enhancement, implying the dissociation of different components of working memory at the hippocampus. Moreover, single trial decoding results suggested that theintracranial field potential response in the right hippocampus can classify the match or switch task. This is consistent with the findings that the right hippocampal activity observed during the simulation of the future events may reflect the encoding of the simulation into memory.展开更多
1|INTRODUCTION Chirality spans over almost every size range,from mole-cules to biological systems and even to galaxies.It is one of the fascinating geometrical properties with a lot of amazing manifestations in the ma...1|INTRODUCTION Chirality spans over almost every size range,from mole-cules to biological systems and even to galaxies.It is one of the fascinating geometrical properties with a lot of amazing manifestations in the material world.As chemi-cal researchers,we are more interested in chirality at the molecular scale and nanoscale.Chiral molecules are found important in life science,agrochemicals,pharma-ceutical industries,biosensing,display materials,and so forth.1–5 Chirality stems from a structure lacking sym-metry elements of inversion symmetry and mirror‐plane,which makes the structure not superimposable with its mirror image.Without these two kinds of symmetries,any structure is chiral,besides conventional chiral organics or spiral inorganic structures.The essence of chirality is the stereochemistry of molecules or nanostructures.展开更多
A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a tradi...A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a traditional RH equipment were evaluated and compared through water modeling experiments and an optimized calculation model.In the water experiments,the mixing time,the residence time and the circulation flow rates were measured,and the flow simulating molten steel in the vacuum was photographed.The results show that the decarburization efficiency in the new RH equipment is much improved.The mixing time is equal to or less than that of the latter when the gas flow rate is higher than 2.33 m^(3)/h.The proportion of the piston flow increases by at least 40%,and the proportion of the well-mixed flow decreases from greater than 40%to less than 20%.The effective flow rate of the new RH equipment increases greatly in the piston flow zone and the total lag flow zone based on the residence time distribution experiment.In conclusion,when a weir is added to a RH vacuum chamber,the effective circulation flow increases significantly,and the decarburization rate KC of molten steel at low-carbon stage is improved.展开更多
Influenza virus (IAV)infection is a major cause of severe respiratory illness that affects almost every country in the world.IAV infections result in respiratory illness and even acute lung injury and death,but the un...Influenza virus (IAV)infection is a major cause of severe respiratory illness that affects almost every country in the world.IAV infections result in respiratory illness and even acute lung injury and death,but the underlying mechanisms responsible for IAV pathogenesis have not yet been fully elucidated.In this study,the basic fibroblast growth factor 2 (FGF2)level was markedly increased in H1N1 virus-infected humans and mice.FGF2,which is predominately derived from epithelial cells,recruits and activates neutrophils via the FGFR2-PI3K-AKT-NFKB signaling pathway.FGF2 depletion or knockout exacerbated influenzaassociated disease by impairing neutrophil recruitment and activation.More importantly,administration of the recombinant FGF2 protein significantly aUeviated the severity of IAV-induced lung injury and promoted the survival of IAV-infected mice.Based on the results from experiments in which neutrophils were depleted and adoptively transferred,FGF2 protected mice against IAV , infection by recruiting neutrophils.Thus,FGF2 plays a critical role in preventing IAV-induced lung injury,and FGF2 is a promising potential therapeutic target during IAV infection.展开更多
Low back pain,mainly caused by intervertebral disc degeneration(IVDD),is a common health problem;however,current surgical treatments are less than satisfactory.Thus,it is essential to develop novel non-invasive surgic...Low back pain,mainly caused by intervertebral disc degeneration(IVDD),is a common health problem;however,current surgical treatments are less than satisfactory.Thus,it is essential to develop novel non-invasive surgical methods for IVDD treatment.Here,we describe a therapeutic strategy to inhibit IVDD by injecting hydrogels modified with the extracellular matrix of costal cartilage(ECM-Gels)that are loaded with cartilage endplate stem cells(CESCs).After loaded with CESCs overexpressing Sphk2(Lenti-Sphk2-CESCs)and injected near the cartilage endplate(CEP)of rats in vivo,ECM-Gels produced Sphk2-engineered exosomes(Lenti-Sphk2-Exos).These exosomes penetrated the annulus fibrosus(AF)and transported Sphk2 into the nucleus pulposus cells(NPCs).Sphk2 activated the phosphatidylinositol 3-kinase(PI3K)/p-AKT pathway as well as the intracellular autophagy of NPCs,ultimately ameliorating IVDD.This study provides a novel and efficient non-invasive combinational strategy for IVDD treatment using injectable ECM-Gels loaded with CESCs that express Sphk2 with sustained release of functional exosomes.展开更多
Tailoring atomic structures of noblemetal nanomaterials with size close to single-unit cell range is essential in both fundamental researchand applications,including their development into high catalytic performance m...Tailoring atomic structures of noblemetal nanomaterials with size close to single-unit cell range is essential in both fundamental researchand applications,including their development into high catalytic performance materials in renewable,green energy conversions,devices for energy storage,and as biosensors for environmental pollutants.However,several strategies used in fabricating these materials still impose enormous challenges,arising from lack of even size distribution,shape uniformity,and controlled composition,which are critical in determining their specific activities and efficiencies.Herein,we report a facile approach for preparing sub-nano-thick palladium nanobelt-based(PdNB)materials.Then we rationalized the formation mechanism of such highly anisotropic structures by morphology-related thermodynamic and kinetic analysis.Moreover,we investigated if electrocatalysis performance of these NB-basedmaterialswere enhanced.Thepalladium(Pd)NBs featured a thickness of∼0.9-1.2 nm and width of 5-18nmwith length extending to severalmicrometers[denoted as Pd(0.9)],or a thickness of∼0.7-0.9 nm and width of 2.5-6 nmwith length of several hundreds of nanometers[denoted as Pd(0.7)].According to our theoretical analysis,one-dimensional(1D)growth encountered almost no energy barrier at optimal reaction conditions,whereas the growth of Pd nanostructures with other dimensions confronted high barriers,indicating that it was plausible to prepare 1D structures with sizes close to single-unit cells.Also,platinum(Pt)could be successfully doped into the Pd(0.9)NBs through a galvanic epitaxial growth,forming edge-Pt-enriched Pd NBs(eePtPd NBs).Further,electron transfer from Pd to Pt imparted the eePtPd NBs with high hydrogen evolution reaction(HER)activity.The eePtPd NBs showed a 3.5 and 1.8 times higher in exchange current density and mass activity(at−0.1 V),respectively,compared to those of Pt catalysts in perchloric acid(HClO_(4))solutions.Finally,the NBs all showed high activity toward ethanol and formic acid oxidation reactions.Our current work aids in gaining insights into tailoring Pd nanostructures at an atomic level and provides Pd sub-nanometric 1D structures for further research.Moreover,our morphology-related thermodynamic and kinetic analysis extend our understanding of the control of nanostructure morphology and might shed light on the precision of designing specific morphologies of noble metal nanocrystal structures.展开更多
Construction of macro-materials with highly oriented microstructures and well-connected interfaces between building blocks is significant for a variety of applications. However, it is still challenging to confine the ...Construction of macro-materials with highly oriented microstructures and well-connected interfaces between building blocks is significant for a variety of applications. However, it is still challenging to confine the desired structures. Thus, well-defined building blocks would be crucial to address this issue. Herein, we present a facile process based on 1.8 nm Pd nanoclusters (NCs) to achieve centimeter-size assemblages with aligned honeycomb structures, where the diameter of a single tubular moiety is -4 μm. Layered and disordered porous assemblages were also obtained by modulating the temperature in this system. The reconciled interactions between the NCs were crucial to the assemblages. As a comparison, 14 nm Pd nanoparticles formed only aggregates. This work highlights the approach of confining the size of the building blocks in order to better control the assembly process and improve the stability of the structures.展开更多
The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With ...The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With telco data and the domain knowledge of an urban city,we are now able to analyze the movement and contact patterns of humans in an unprecedented scale.Flow map is widely used to display the movements of humans from one single source to multiple destinations by representing locations as nodes and movements as edges.However,it fails the task of visualizing both movement and contact data.In addition,analysts often need to compare and examine the patterns side by side,and do various quantitative analysis.In this work,we propose a novel spatio-temporal flow map layout to visualize when and where people from different locations move into the same places and make contact.We also propose integrating the spatiotemporal flow maps into existing spatiotemporal visualization techniques to form a suite of techniques for visualizing the movement and contact patterns.We report a potential application the proposed techniques can be applied to.The results show that our design and techniques properly unveil hidden information,while analysis can be achieved efficiently.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51374081)
文摘Droplet coalescence in liquid steel was carefully investigated through observations of the distribution pattern of inclusions in solidified steel samples. The process of droplet coalescence was slow, and the critical Weber number(We) was used to evaluate the coalescence or separation of droplets. The relationship between the collision parameter and the critical We indicated whether slow coalescence or bouncing of droplets occurred. The critical We was 5.5, which means that the droplets gradually coalesce when We ≤ 5.5, whereas they bounce when We > 5.5. For the carbonate wire feeding into liquid steel, a mathematical model implementing a combined computational fluid dynamics(CFD)–discrete element method(DEM) approach was developed to simulate the movement and coalescence of variably sized droplets in a bottom-argon-blowing ladle. In the CFD model, the flow field was solved on the premise that the fluid was a continuous medium. Meanwhile, the droplets were dispersed in the DEM model, and the coalescence criterion of the particles was added to simulate the collision-coalescence process of the particles. The numerical simulation results and observations of inclusion coalescence in steel samples are consistent.
基金financial support through the StartUp Fund for Outstanding Talent with grant number A1098531023601307the National University of Singapore and Ministry of Education in Singapore for its financial support through Tier-1 projects with grant numbers R-279000-622-133 and R-279-000-622-731.
文摘Electrocatalytic carb on dioxide reducti on(CO_(2)R)presents a promising route to establish zero-e mission carb on cycle and store in termittent ren ewable energy into chemical fuels for steady energy supply.Methanol is an ideal energy carrier as alternative fuels and one of the most important commodity chemicals.Nevertheless,methanol is currently mainly produced from fossil-based syngas,the production of which yields tremendous carb on emission globally.Direct CO_(2)R towards metha nol poses great potential to shift the paradigm of methanol production.In this perspective,we focus our discussions on producing methanol from electrochemical CO_(2)R,using metallomacrocyclic molecules as the model catalysts.We discuss the motivation of having methanol as the sole CO_(2)R product,the documented application of metallomacrocyclic catalysts for CO_(2)R,and recent advance in catalyzing CO_(2) to methanol with cobalt phthalocyanine-based catalysts.We attempt to understand the key factors in determining the activity,selectivity,and stability of electrocatalytic CO_(2)-to-methanol conversion,and to draw mechanistic insights from existing observations.Finally,we identify the challenges hindering methanol electrosynthesis directly from CO_(2) and some intriguing directions worthy of further investigation and exploration.
基金supported by grants from the Ministry of Science and Technology of China (2015CB351701 and 2012CB825500)the National Natural Science Foundation of China (91132302)the Chinese Academy of Sciences (XDB2010001 and XDB2050001)
文摘A previous functional magnetic resonance imaging study reported evidence for parallel memory traces in the hippocampus: a controlled match signal detecting matches to internally-generated goal states and an automatic mismatch signal identifying unpredicted perceptual novelty. However, the timing information in this process is unknown. In the current study, facilitated by the high spatial and temporal resolution of intracranial recording from human patients, we confirmed that the left posterior hippocampus played an important role in the goal match enhancement effect, in which combinations of object identity and location were involved. We also found that this effect happened within 520 ms to 735 ms after the probe onset, *150 ms later than the perceptual mismatch enhancement found bilaterally in both the anterior and posterior hippocampus. More specifically, the latency of the perceptual mismatch enhancement effect of the right hippocampus was positively correlated with the performance accuracy. These results suggested that the hippocampus is crucial in working memory if features binding with location are involved in the task and the goal match enhancement effect happens after perceptual mismatch enhancement, implying the dissociation of different components of working memory at the hippocampus. Moreover, single trial decoding results suggested that theintracranial field potential response in the right hippocampus can classify the match or switch task. This is consistent with the findings that the right hippocampal activity observed during the simulation of the future events may reflect the encoding of the simulation into memory.
文摘1|INTRODUCTION Chirality spans over almost every size range,from mole-cules to biological systems and even to galaxies.It is one of the fascinating geometrical properties with a lot of amazing manifestations in the material world.As chemi-cal researchers,we are more interested in chirality at the molecular scale and nanoscale.Chiral molecules are found important in life science,agrochemicals,pharma-ceutical industries,biosensing,display materials,and so forth.1–5 Chirality stems from a structure lacking sym-metry elements of inversion symmetry and mirror‐plane,which makes the structure not superimposable with its mirror image.Without these two kinds of symmetries,any structure is chiral,besides conventional chiral organics or spiral inorganic structures.The essence of chirality is the stereochemistry of molecules or nanostructures.
文摘A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a traditional RH equipment were evaluated and compared through water modeling experiments and an optimized calculation model.In the water experiments,the mixing time,the residence time and the circulation flow rates were measured,and the flow simulating molten steel in the vacuum was photographed.The results show that the decarburization efficiency in the new RH equipment is much improved.The mixing time is equal to or less than that of the latter when the gas flow rate is higher than 2.33 m^(3)/h.The proportion of the piston flow increases by at least 40%,and the proportion of the well-mixed flow decreases from greater than 40%to less than 20%.The effective flow rate of the new RH equipment increases greatly in the piston flow zone and the total lag flow zone based on the residence time distribution experiment.In conclusion,when a weir is added to a RH vacuum chamber,the effective circulation flow increases significantly,and the decarburization rate KC of molten steel at low-carbon stage is improved.
基金funding from the National High Technology Research and Development Program of China (SS2015AA020924)the National Natural Science Foundation of China (81771700)+2 种基金the Ministry of Science and Technology of China (2013ZXI0004003 and SS2012AA020905)the National Major Research and Development Program (2016YFA0502203 and 2017YFC1200800)P.Y.was supported by the Beijing Nova Program (Z141107001814054).
文摘Influenza virus (IAV)infection is a major cause of severe respiratory illness that affects almost every country in the world.IAV infections result in respiratory illness and even acute lung injury and death,but the underlying mechanisms responsible for IAV pathogenesis have not yet been fully elucidated.In this study,the basic fibroblast growth factor 2 (FGF2)level was markedly increased in H1N1 virus-infected humans and mice.FGF2,which is predominately derived from epithelial cells,recruits and activates neutrophils via the FGFR2-PI3K-AKT-NFKB signaling pathway.FGF2 depletion or knockout exacerbated influenzaassociated disease by impairing neutrophil recruitment and activation.More importantly,administration of the recombinant FGF2 protein significantly aUeviated the severity of IAV-induced lung injury and promoted the survival of IAV-infected mice.Based on the results from experiments in which neutrophils were depleted and adoptively transferred,FGF2 protected mice against IAV , infection by recruiting neutrophils.Thus,FGF2 plays a critical role in preventing IAV-induced lung injury,and FGF2 is a promising potential therapeutic target during IAV infection.
基金supported by the National Natural Science Foundation of China(Grant Number:81874028,81702182)the Research Program of Foundation Science and Application Technology of Chongqing(Grant Number:cstc2018jcyjAX0598)Basic Medical College Foundation of Army Medical University(2019JCZX10).
文摘Low back pain,mainly caused by intervertebral disc degeneration(IVDD),is a common health problem;however,current surgical treatments are less than satisfactory.Thus,it is essential to develop novel non-invasive surgical methods for IVDD treatment.Here,we describe a therapeutic strategy to inhibit IVDD by injecting hydrogels modified with the extracellular matrix of costal cartilage(ECM-Gels)that are loaded with cartilage endplate stem cells(CESCs).After loaded with CESCs overexpressing Sphk2(Lenti-Sphk2-CESCs)and injected near the cartilage endplate(CEP)of rats in vivo,ECM-Gels produced Sphk2-engineered exosomes(Lenti-Sphk2-Exos).These exosomes penetrated the annulus fibrosus(AF)and transported Sphk2 into the nucleus pulposus cells(NPCs).Sphk2 activated the phosphatidylinositol 3-kinase(PI3K)/p-AKT pathway as well as the intracellular autophagy of NPCs,ultimately ameliorating IVDD.This study provides a novel and efficient non-invasive combinational strategy for IVDD treatment using injectable ECM-Gels loaded with CESCs that express Sphk2 with sustained release of functional exosomes.
基金This work was supported by the National Key R&D Program of China(2017YFA0700101 and 2016YFA0202801)NSFC(21431003 and 21521091).
文摘Tailoring atomic structures of noblemetal nanomaterials with size close to single-unit cell range is essential in both fundamental researchand applications,including their development into high catalytic performance materials in renewable,green energy conversions,devices for energy storage,and as biosensors for environmental pollutants.However,several strategies used in fabricating these materials still impose enormous challenges,arising from lack of even size distribution,shape uniformity,and controlled composition,which are critical in determining their specific activities and efficiencies.Herein,we report a facile approach for preparing sub-nano-thick palladium nanobelt-based(PdNB)materials.Then we rationalized the formation mechanism of such highly anisotropic structures by morphology-related thermodynamic and kinetic analysis.Moreover,we investigated if electrocatalysis performance of these NB-basedmaterialswere enhanced.Thepalladium(Pd)NBs featured a thickness of∼0.9-1.2 nm and width of 5-18nmwith length extending to severalmicrometers[denoted as Pd(0.9)],or a thickness of∼0.7-0.9 nm and width of 2.5-6 nmwith length of several hundreds of nanometers[denoted as Pd(0.7)].According to our theoretical analysis,one-dimensional(1D)growth encountered almost no energy barrier at optimal reaction conditions,whereas the growth of Pd nanostructures with other dimensions confronted high barriers,indicating that it was plausible to prepare 1D structures with sizes close to single-unit cells.Also,platinum(Pt)could be successfully doped into the Pd(0.9)NBs through a galvanic epitaxial growth,forming edge-Pt-enriched Pd NBs(eePtPd NBs).Further,electron transfer from Pd to Pt imparted the eePtPd NBs with high hydrogen evolution reaction(HER)activity.The eePtPd NBs showed a 3.5 and 1.8 times higher in exchange current density and mass activity(at−0.1 V),respectively,compared to those of Pt catalysts in perchloric acid(HClO_(4))solutions.Finally,the NBs all showed high activity toward ethanol and formic acid oxidation reactions.Our current work aids in gaining insights into tailoring Pd nanostructures at an atomic level and provides Pd sub-nanometric 1D structures for further research.Moreover,our morphology-related thermodynamic and kinetic analysis extend our understanding of the control of nanostructure morphology and might shed light on the precision of designing specific morphologies of noble metal nanocrystal structures.
文摘Construction of macro-materials with highly oriented microstructures and well-connected interfaces between building blocks is significant for a variety of applications. However, it is still challenging to confine the desired structures. Thus, well-defined building blocks would be crucial to address this issue. Herein, we present a facile process based on 1.8 nm Pd nanoclusters (NCs) to achieve centimeter-size assemblages with aligned honeycomb structures, where the diameter of a single tubular moiety is -4 μm. Layered and disordered porous assemblages were also obtained by modulating the temperature in this system. The reconciled interactions between the NCs were crucial to the assemblages. As a comparison, 14 nm Pd nanoparticles formed only aggregates. This work highlights the approach of confining the size of the building blocks in order to better control the assembly process and improve the stability of the structures.
基金This project is partially funded by a grant(Ref:YBCB2009041-44)Huawei Technologies Noah’s Ark Lab and also grant HK RGC GRF 16241916.
文摘The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With telco data and the domain knowledge of an urban city,we are now able to analyze the movement and contact patterns of humans in an unprecedented scale.Flow map is widely used to display the movements of humans from one single source to multiple destinations by representing locations as nodes and movements as edges.However,it fails the task of visualizing both movement and contact data.In addition,analysts often need to compare and examine the patterns side by side,and do various quantitative analysis.In this work,we propose a novel spatio-temporal flow map layout to visualize when and where people from different locations move into the same places and make contact.We also propose integrating the spatiotemporal flow maps into existing spatiotemporal visualization techniques to form a suite of techniques for visualizing the movement and contact patterns.We report a potential application the proposed techniques can be applied to.The results show that our design and techniques properly unveil hidden information,while analysis can be achieved efficiently.