Bacillus subtilis is a non-pathogenic Gram-positive bacterium that has been widely used to produce industrially and pharmaceutically relevant proteins.Trehalose,a non reducing disaccharide used as protective agent and...Bacillus subtilis is a non-pathogenic Gram-positive bacterium that has been widely used to produce industrially and pharmaceutically relevant proteins.Trehalose,a non reducing disaccharide used as protective agent and additive in foodstuffs and pharmaceutical products,can be prepared by trehalose synthase(TreS).The present work aims to construct a robust recombinant B.subtilis to achieve the secretory expression of TreS.In this study,the treS gene from Pseudomonas putida ATCC47054 was amplified by PCR and further cloned and expressed in B.subtilis WB800 N using pHT01 as expression vector.For avoiding the use of inducer,promoter P_(srfA)was used to replace the promoter P_(grac)in pHT01 and verify the activity of recombinant trehalose synthase.The TreS activity assay was employed to evaluate the performance of recombinant B.subtilis W800 N under different phosphate concentrations,carbon sources,carbon source concentrations,nitrogen sources and pH.The results showed that the P_(srfA)promoter had a good regulation effect under pH 8.0 condition,and the enzyme activity reached 6000 U/L.Using the PhoD as the secretory signal peptide,TreS was effectively secreted,and the extracellular enzyme activity reached 2100 U/L,accounting for 35%of the total enzyme activity.By optimizing the medium and fermentation conditions,the extracellular enzyme activity reached 6900 U/L in 5 L of fermentor,and the proportion reached 48%.The pHT01-P_(srfA)-PhoD-treS secretory recombinant B.subtilis constructed in this study has great potential in trehalose synthase production.展开更多
A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,pre...A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,previous counter-I_(p)NBI injections are upgraded to co-I_(p)injections.Analysis shows that due to the reversed direction of drift across the flux surfaces caused by the pitch angle,the beam prompt loss fraction decreases from about 49%to 3%after the upgrade.Moreover,because of the change of entire beam path,beam shine-through(ST)loss fraction for counter-I_(p)tangential and counter-I_(p)perpendicular injections is reversed to co-I_(p)tangential and co-I_(p)perpendicular injections,respectively.Due to the change in the initial trapped-confined beam ion fraction caused by the peaked pitch profiles,the losses induced by toroidal ripple field are also reversed after the upgrade.To further improve the beam-ion confinement under the present NBI layout,the amplitudes of toroidal field are increased from 1.75 to 2.20 T.Result shows that,due to the smaller orbit width and peaked pitch angle profile,the beam prompt loss power is lower with higher toroidal field.Due to the synergy of higher initial trapped-confined beam ion fraction and narrower Goldston-White-Boozer(GWB)boundary,the loss induced by ripple diffusion is higher with higher toroidal field.The combined effect of beam ST loss,prompt loss and ripple loss,contributes to the increase in beam ion density.The decrease in beam loss power enhances beam heating efficiency,especially the fraction of beam heating ions.Finally,comparison between simulation and measurement by^(235)U fission chamber(FC)indicates that the increase in neutron rate is mainly contributed by improvement of beam-ion confinement.This study can provide potential support for beam operation and high-T_(i)experiment on EAST tokamak.展开更多
Electrides are unique materials,whose anionic electrons are confined to interstitial voids,and they have broad potential applications in various areas.In contrast to the majority of inorganic electrides,in which the a...Electrides are unique materials,whose anionic electrons are confined to interstitial voids,and they have broad potential applications in various areas.In contrast to the majority of inorganic electrides,in which the anionic electrons primarily consist of s-electrons of metals,electrides with anionic d-electrons are very rare.Based on first-principles electronic structure calculations,we predict that the layered transition metal chalcogenide Hf_(2)Se is a novel electride candidate with anionic d-electrons.Our results indicate that the anionic electrons confined in the Hf_(6) octahedra vacancy between [Hf_(2)Se] layers mainly come from the Hf-5 d orbitals.In addition,the anionic electrons coexist with the Hf-Hf multiple-center metallic bonds located in the center of neighboring Hf_(4) tetrahedra.The calculated work function(3.33 eV) for the(110) surface of Hf_(2)Se is slightly smaller than that of Hf_(2)S,which has recently been reported to exhibit good electrocatalytic performance.Our study of Hf2 Se will enrich the electride family,and promote further research into the physical properties and applications of electrides.展开更多
Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@sh...Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@shell structure SiO_(2)@C adopting SiO_(2)nanospheres as a hard template.The acquired SiO_(2)@C nanocomposites displayed unsatisfied EMW absorption performances with minimum reflection loss value of-34.92 dB at 6.35 mm,and effective absorption bandwidth value of 3.20 GHz at 4.83 mm,respectively.In order to further comprehensively boost its microwave absorption performances(MAPs),a facile self-assembly strategy was adopted to load Au nanoparticles on the outer surface of SiO_(2)@C nanospheres,constructing core@shell SiO_(2)@C-Au multicomponent nanocomposites(MCNCs).By regulating the volume of Au nanoparticles,different Au contents of SiO_(2)@C-Au MCNCs could be selectively produced in high efficiencies.The obtained outcomes demonstrated that the SiO_(2)@C-Au MCNCs presented improved properties including EMW attenuation,impedance matching,conduction loss and polarization loss with increasing the content of Au nanoparticles.Thanks to the introduction of conductive Au nanoparticles and excellent interfacial effects,the SiO_(2)@C-Au MCNCs presented the greatly improved antimicrobial and EMW absorption performances including strong absorption,wide bandwidth and small thicknesses.Consequently,this finding offered a novel strategy to construct core@shell SiO_(2)@C-Au MCNCs,which simultaneously boosted conduction and polarization loss capabilities for EMW absorption.展开更多
基金Supported by the National Nature Science Foundation of China(No.31501413)Shandong key project of Research&Development plan(No.2017GSF221019)+1 种基金Young doctorate Cooperation Fund Project,Qi Lu University of Technology(Shandong Academy of Sciences)(No.2017BSHZ021)Shandong Natural Science Foundation Project(ZR2017BC072)
文摘Bacillus subtilis is a non-pathogenic Gram-positive bacterium that has been widely used to produce industrially and pharmaceutically relevant proteins.Trehalose,a non reducing disaccharide used as protective agent and additive in foodstuffs and pharmaceutical products,can be prepared by trehalose synthase(TreS).The present work aims to construct a robust recombinant B.subtilis to achieve the secretory expression of TreS.In this study,the treS gene from Pseudomonas putida ATCC47054 was amplified by PCR and further cloned and expressed in B.subtilis WB800 N using pHT01 as expression vector.For avoiding the use of inducer,promoter P_(srfA)was used to replace the promoter P_(grac)in pHT01 and verify the activity of recombinant trehalose synthase.The TreS activity assay was employed to evaluate the performance of recombinant B.subtilis W800 N under different phosphate concentrations,carbon sources,carbon source concentrations,nitrogen sources and pH.The results showed that the P_(srfA)promoter had a good regulation effect under pH 8.0 condition,and the enzyme activity reached 6000 U/L.Using the PhoD as the secretory signal peptide,TreS was effectively secreted,and the extracellular enzyme activity reached 2100 U/L,accounting for 35%of the total enzyme activity.By optimizing the medium and fermentation conditions,the extracellular enzyme activity reached 6900 U/L in 5 L of fermentor,and the proportion reached 48%.The pHT01-P_(srfA)-PhoD-treS secretory recombinant B.subtilis constructed in this study has great potential in trehalose synthase production.
基金supported by the National Key R&D Program of China(No.2019YFE03020004)National Natural Science Foundation of China(Nos.12175272 and 12347186)+3 种基金Anhui Provincial Natural Science Foundation(No.2008085J04)Anhui Provincial Key R&D Program(No.202104b11020003)Collaborative Innovation Program of Hefei Science Center,CAS(No.YZJJ2023QN17)State Key Laboratory of Advanced Electromagnetic Technology(No.AET 2024KF010)。
文摘A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,previous counter-I_(p)NBI injections are upgraded to co-I_(p)injections.Analysis shows that due to the reversed direction of drift across the flux surfaces caused by the pitch angle,the beam prompt loss fraction decreases from about 49%to 3%after the upgrade.Moreover,because of the change of entire beam path,beam shine-through(ST)loss fraction for counter-I_(p)tangential and counter-I_(p)perpendicular injections is reversed to co-I_(p)tangential and co-I_(p)perpendicular injections,respectively.Due to the change in the initial trapped-confined beam ion fraction caused by the peaked pitch profiles,the losses induced by toroidal ripple field are also reversed after the upgrade.To further improve the beam-ion confinement under the present NBI layout,the amplitudes of toroidal field are increased from 1.75 to 2.20 T.Result shows that,due to the smaller orbit width and peaked pitch angle profile,the beam prompt loss power is lower with higher toroidal field.Due to the synergy of higher initial trapped-confined beam ion fraction and narrower Goldston-White-Boozer(GWB)boundary,the loss induced by ripple diffusion is higher with higher toroidal field.The combined effect of beam ST loss,prompt loss and ripple loss,contributes to the increase in beam ion density.The decrease in beam loss power enhances beam heating efficiency,especially the fraction of beam heating ions.Finally,comparison between simulation and measurement by^(235)U fission chamber(FC)indicates that the increase in neutron rate is mainly contributed by improvement of beam-ion confinement.This study can provide potential support for beam operation and high-T_(i)experiment on EAST tokamak.
基金Supported by the National Natural Science Foundation of China(Grant No.11774424)the Fundamental Research Funds for the Central Universities(Grant No.2017RC20)+3 种基金the Research Funds of Renmin University of China(Grant No.20XNH064)the CAS Interdisciplinary Innovation Teamthe Beijing Natural Science Foundation(Grant No.Z200005)the Research Innovation Fund for College Students of Beijing University of Posts and Telecommunications。
文摘Electrides are unique materials,whose anionic electrons are confined to interstitial voids,and they have broad potential applications in various areas.In contrast to the majority of inorganic electrides,in which the anionic electrons primarily consist of s-electrons of metals,electrides with anionic d-electrons are very rare.Based on first-principles electronic structure calculations,we predict that the layered transition metal chalcogenide Hf_(2)Se is a novel electride candidate with anionic d-electrons.Our results indicate that the anionic electrons confined in the Hf_(6) octahedra vacancy between [Hf_(2)Se] layers mainly come from the Hf-5 d orbitals.In addition,the anionic electrons coexist with the Hf-Hf multiple-center metallic bonds located in the center of neighboring Hf_(4) tetrahedra.The calculated work function(3.33 eV) for the(110) surface of Hf_(2)Se is slightly smaller than that of Hf_(2)S,which has recently been reported to exhibit good electrocatalytic performance.Our study of Hf2 Se will enrich the electride family,and promote further research into the physical properties and applications of electrides.
基金support from Guizhou Provincial Basic Research Program(Natural Science)(No.ZD[2025]Key 086)Platform of Science and Technology and Talent Team Plan of Guizhou province(No.GCC[2023]007)Innovation Group of Guizhou University(No.[2024]08)for financial support.
文摘Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@shell structure SiO_(2)@C adopting SiO_(2)nanospheres as a hard template.The acquired SiO_(2)@C nanocomposites displayed unsatisfied EMW absorption performances with minimum reflection loss value of-34.92 dB at 6.35 mm,and effective absorption bandwidth value of 3.20 GHz at 4.83 mm,respectively.In order to further comprehensively boost its microwave absorption performances(MAPs),a facile self-assembly strategy was adopted to load Au nanoparticles on the outer surface of SiO_(2)@C nanospheres,constructing core@shell SiO_(2)@C-Au multicomponent nanocomposites(MCNCs).By regulating the volume of Au nanoparticles,different Au contents of SiO_(2)@C-Au MCNCs could be selectively produced in high efficiencies.The obtained outcomes demonstrated that the SiO_(2)@C-Au MCNCs presented improved properties including EMW attenuation,impedance matching,conduction loss and polarization loss with increasing the content of Au nanoparticles.Thanks to the introduction of conductive Au nanoparticles and excellent interfacial effects,the SiO_(2)@C-Au MCNCs presented the greatly improved antimicrobial and EMW absorption performances including strong absorption,wide bandwidth and small thicknesses.Consequently,this finding offered a novel strategy to construct core@shell SiO_(2)@C-Au MCNCs,which simultaneously boosted conduction and polarization loss capabilities for EMW absorption.
