AIM: To develop a simple and convenient method for extracting genomic DNA from intestinal microflora for en- terobacterial repetitive intergenic consensus (ERIC)-PCR detection. METHODS: Five methods of extracting bact...AIM: To develop a simple and convenient method for extracting genomic DNA from intestinal microflora for en- terobacterial repetitive intergenic consensus (ERIC)-PCR detection. METHODS: Five methods of extracting bacterial DNA, including Tris-EDTA buffer, chelex-100, ultrapure water, 2% sodium dodecyl sulfate and 10% Triton-100 with and without sonication, were compared with the commercial fecal DNA extraction kit method, which is considered as the gold standard for DNA extraction. The comparison was based on the yield and purity of DNA and the indexes of the structure and property of micro-organisms that were reflected by ERIC-PCR. RESULTS: The yield and purity of DNA obtained by the chelex method was similar to that obtained with the fecal DNA kit. The ERIC-PCR results obtained for the DNA extracted by the chelex method and those obtained for DNA extracted with the fecal DNA kit were basically the same.CONCLUSION: The chelex method is recommended for ERIC-PCR experiments in view of its simplicity and cost- effectiveness; and it is suitable for extracting total DNA from intestinal micro-organisms, particularly for handling a large number of samples.展开更多
Cerium and titanium were added to an A1-42Zn-5.5Si brazing alloy, and the subsequent microstructures of the brazing alloy and the 6061 AI alloy brazing seam were investigated. The microstructures of filler metals and ...Cerium and titanium were added to an A1-42Zn-5.5Si brazing alloy, and the subsequent microstructures of the brazing alloy and the 6061 AI alloy brazing seam were investigated. The microstructures of filler metals and brazed joints were characterized by scanning elec- tron microscopy and X-ray energy dispersion spectrometry. A new Ce-Ti phase formed around the silicon phase in the modified filler metal and this saturation phenomenon was analyzed. Interestingly, following brazing of the 6061 alloy, there is no evidence of the Ce--Ti phase in the brazing seam. Because of the mutual solubility of the brazing alloy and base metal, the quantity of the solvent increases, and the solute Ce and Ti atoms assume an undersaturated state.展开更多
We previously demonstrated that administering 2-（2-benzofuranyl）-2-imidazolin（2-BFI）, an imidazoline I2 receptor agonist, immediately after ischemia onset can protect the brain from ischemic insult. However, immed...We previously demonstrated that administering 2-（2-benzofuranyl）-2-imidazolin（2-BFI）, an imidazoline I2 receptor agonist, immediately after ischemia onset can protect the brain from ischemic insult. However, immediate administration after stroke is difficult to realize in the clinic. Thus, the therapeutic time window of 2-BFI should be determined. Sprague-Dawley rats provided by Wenzhou Medical University in China received right middle cerebral artery occlusion for 120 minutes, and were treated with 2-BFI（3 mg/kg） through the caudal vein at 0, 1, 3, 5, 7, and 9 hours after reperfusion. Neurological function was assessed using the Longa＇s method. Infarct volume was measured by 2,3,5-triphenyltetrazolium chloride assay. Morphological changes in the cortical penumbra were observed by hematoxylin-eosin staining under transmission electron microscopy. The apoptosis levels in the ipsilateral cortex were examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling（TUNEL） assay. The protein expression of Bcl-2 and BAX was detected using immunohistochemistry. We found the following： Treatment with 2-BFI within 5 hours after reperfusion obviously improved neurological function. Administering 2-BFI within 9 hours after ischemia/reperfusion decreased infarct volume and alleviated apoptosis. 2-BFI administration at different time points after reperfusion alleviated the pathological damage of the ischemic penumbra and reduced the number of apoptotic neurons, but the protective effect was more obvious when administered within 5 hours. Administration of 2-BFI within 5 hours after reperfusion remarkably increased Bcl-2 expression and decreased BAX expression. To conclude, 2-BFI shows potent neuroprotective effects when administered within 5 hours after reperfusion, seemingly by up-regulating Bcl-2 and down-regulating BAX expression. The time window provided clinical potential for ischemic stroke by 2-BFI.展开更多
Based on density functional theory calculations,the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene(Pt1/Gr-O)is investigated.It is suggested...Based on density functional theory calculations,the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene(Pt1/Gr-O)is investigated.It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B-H bonds breaking.Then one H2O molecule attacks the left*BHNH3 group(*represents adsorbed state)to form*BH(H2O)NH3 and the elongated O-H bond is easily broken to produce*BH(OH)NH3.The second H2O molecule attacks*BH(OH)NH3 to form*BH(OH)(H2O)NH3 and the breaking of O-H bond pointing to the plane of Pt1/Gr-O results in the desorption of BH(OH)2NH3.The second hydrogen molecule is produced from two hydrogen atoms coming from two H2O molecules and Pt1/Gr-O is recovered after the releasing of hydrogen molecule.The third hydrogen molecule is generated by the further hydrolysis of BH(OH)2NH3 in water solution.The rate-limiting step of the whole process is the combination of one H2O molecule and*BHNH3 with an energy barrier of 16.1 kcal/mol.Thus,Pt1/Gr-O is suggested to be a promising catalyst for hydrolysis of NH3BH3 at room temperature.展开更多
Using first-principles calculations, we studied the interaction of methanol with the Pt（100） surface based on generalized gradient approximation. We found that top sites of Pt（100） surface are the favored adsorpti...Using first-principles calculations, we studied the interaction of methanol with the Pt（100） surface based on generalized gradient approximation. We found that top sites of Pt（100） surface are the favored adsorptive positions in energy, and methanol molecule interacts with the Pt surface through oxygen atoms. Moreover, we also explored the possible dissociation pathways of methanol on the Pt surface, and suggested that the products of dissociation can be controlled by the external manipulation.展开更多
KSSOLV(Kohn-Sham Solver)is a MATLAB(Matrix Laboratory)toolbox for solving the Kohn-Sham density functional theory(KS-DFT)with the plane-wave basis set.In the KS-DFT calculations,the most expensive part is commonly the...KSSOLV(Kohn-Sham Solver)is a MATLAB(Matrix Laboratory)toolbox for solving the Kohn-Sham density functional theory(KS-DFT)with the plane-wave basis set.In the KS-DFT calculations,the most expensive part is commonly the diagonalization of Kohn-Sham Hamiltonian in the self-consistent field(SCF)scheme.To enable a personal computer to perform medium-sized KS-DFT calculations that contain hundreds of atoms,we present a hybrid CPU-GPU implementation to accelerate the iterative diagonalization algorithms implemented in KSSOLV by using the MATLAB built-in Parallel Computing Toolbox.We compare the performance of KSSOLV-GPU on three types of GPU,including RTX3090,V100,and A100,with conventional CPU implementation of KSSOLV respectively and numerical results demonstrate that hybrid CPU-GPU implementation can achieve a speedup of about 10 times compared with sequential CPU calculations for bulk silicon systems containing up to 128 atoms.展开更多
FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and ele...FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs^- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that, in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.展开更多
The geometrical and electronic properties of the anionic and neutral V2O6 clusters were studied with the spin unrestricted hybrid density functional B3LYP method. The calculated ground states of both clusters are diff...The geometrical and electronic properties of the anionic and neutral V2O6 clusters were studied with the spin unrestricted hybrid density functional B3LYP method. The calculated ground states of both clusters are different from the previous theoretical results. The ground state of V2O6^- is found to be a doublet with C2v symmetry, while a doublet with D2h symmetry was previously obtained by Vyboishchikov and Sauer. For neutral V206, the ground state is an open-shell singlet with D2h symmetry whose energy is very close to that of the triplet state. In contrast, a closed-shell singlet with D2h symmetry was obtained by Vyboishchikov and Sauer, and Calatayud et al. found a triplet ground state with Cs symmetry. Moreover, the calculated adiabatic and vertical detachment energies of the anion cluster are in much better agreement with the experimental results of photoelectron spectroscopy than previous theoretical values.展开更多
To the Editor:Autonomic dysfunction is an important factor in the pathogenesis of unstable angina pectoris (UAP).It affects coronary artery systolic function,induces coronary spasm,aggravates myocardial ischemia,reduc...To the Editor:Autonomic dysfunction is an important factor in the pathogenesis of unstable angina pectoris (UAP).It affects coronary artery systolic function,induces coronary spasm,aggravates myocardial ischemia,reduces ventricular fibrillation threshold,and increases the incidence of sudden cardiac death in UAP.展开更多
Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on t...Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on the properties of porous Si_(3)N_(4) ceramics were investigated.Onlyβ-Si_(3)N_(4) phase is observed in porous Si_(3)N_(4) ceramics,and Si_(3)N_(4) PHMs distribute uniformly both in Si_(3)N_(4) green samples and porous Si_(3)N_(4) ceramics.Results show that solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content could considerably influence the properties of porous Si_(3)N_(4) ceramics.With the increase of solid loading of Si_(3)N_(4) slurry(decrease of Si_(3)N_(4) PHM content),the distributing state of Si_(3)N_(4) PHMs changes from contacting with each other to just embedding in the matrix,thus their porosity decreases,while their shrinkage,flexural strength,and fracture toughness increase.展开更多
Polymer microspheres with uniform size,composition,and surface property have gained extensive researches in past decades.Conventional bottom-up approaches are using monomers or oligomers to build up desired polymer mi...Polymer microspheres with uniform size,composition,and surface property have gained extensive researches in past decades.Conventional bottom-up approaches are using monomers or oligomers to build up desired polymer microspheres.However,directly shaping high-molecular-weight polymers into well-ordered polymer microspheres remains a great challenge.Herein,we reported a facile and efficient top-down approach tofabricate microspheres with high-molecular-weight polymer microfibers.By harnessing interfacial engineering-control during the polymer microspheres formation,uniformly sized microspheres could be produced with widely ranged diameters(from 10μm to the capillary length of each polymer melt).The size limitation of this approach could be further extended by a controllable Plateau-Rayleigh instability phenomenon.Principally,the top-down approach allows fabrication of microspheres by various polymer melts with surface energy higher than 25 mN/m.Our work paves a way for green,cost-effective,and customizable production of a variety of functional polymer microspheres without any chemical reaction assistant.展开更多
In this paper, novel Al2O3-based poly-hollow microsphere (PHM) ceramics were prepared using Si3N4 and Al2O3 PHMs as pore-forming agents. The effect of Si3N4 and Al2O3 PHMs with different percentages on properties of A...In this paper, novel Al2O3-based poly-hollow microsphere (PHM) ceramics were prepared using Si3N4 and Al2O3 PHMs as pore-forming agents. The effect of Si3N4 and Al2O3 PHMs with different percentages on properties of Al2O3-based PHM ceramics was investigated. Through adjusting percentage of Al2O3 PHMs, Al2O3-based PHM ceramics with enhanced properties are achieved. X-ray diffraction (XRD) results show that main phases of Al2O3-based PHM ceramics vary from beta-SiAlON (z value increases from 2.9 to 4) to Al2O3 with the increase of percentage of Al2O3 PHMs from 10% to 100%. The different phase compositions result in different properties of Al2O3-based PHM ceramics. With the increase of percentage of Al2O3 PHMs, porosity of Al2O3-based PHM ceramics gradually decreases, while their shrinkage, flexural strength, and fracture toughness firstly decrease and then increase. Using different kinds of ceramic PHMs as pore-forming agents, various novel and high-performance porous ceramics could be prepared via optimizing percentage of ceramic PHMs in the future.展开更多
基金The National Science Technology Pillar Program, 2007Z06-017Program for New Century Outstanding Talents from Universities, NCET-04-0906/NCET-06-0818+1 种基金Sichuan Provincial Basic Research Program, 04JY029-006-1/04JY021-100/07JY029-017Program for Key Disciplines Construction of Sichuan Province, SZD0418
文摘AIM: To develop a simple and convenient method for extracting genomic DNA from intestinal microflora for en- terobacterial repetitive intergenic consensus (ERIC)-PCR detection. METHODS: Five methods of extracting bacterial DNA, including Tris-EDTA buffer, chelex-100, ultrapure water, 2% sodium dodecyl sulfate and 10% Triton-100 with and without sonication, were compared with the commercial fecal DNA extraction kit method, which is considered as the gold standard for DNA extraction. The comparison was based on the yield and purity of DNA and the indexes of the structure and property of micro-organisms that were reflected by ERIC-PCR. RESULTS: The yield and purity of DNA obtained by the chelex method was similar to that obtained with the fecal DNA kit. The ERIC-PCR results obtained for the DNA extracted by the chelex method and those obtained for DNA extracted with the fecal DNA kit were basically the same.CONCLUSION: The chelex method is recommended for ERIC-PCR experiments in view of its simplicity and cost- effectiveness; and it is suitable for extracting total DNA from intestinal micro-organisms, particularly for handling a large number of samples.
基金financially supported by the National Natural Science Foundation of China(No.51375233)
文摘Cerium and titanium were added to an A1-42Zn-5.5Si brazing alloy, and the subsequent microstructures of the brazing alloy and the 6061 AI alloy brazing seam were investigated. The microstructures of filler metals and brazed joints were characterized by scanning elec- tron microscopy and X-ray energy dispersion spectrometry. A new Ce-Ti phase formed around the silicon phase in the modified filler metal and this saturation phenomenon was analyzed. Interestingly, following brazing of the 6061 alloy, there is no evidence of the Ce--Ti phase in the brazing seam. Because of the mutual solubility of the brazing alloy and base metal, the quantity of the solvent increases, and the solute Ce and Ti atoms assume an undersaturated state.
基金supported by the National Natural Science Foundation of China,No.81571114 and 81771267(to ZH)the National Science Funds for Distinguished Youth Scholars of China,No.81325007(to XMJ)+2 种基金the Distinguished Professor of Cheung Kong Scholars Program in China,No.T2014251(to XMJ)the Wenzhou Municipal Sci-Tec Bureau Programs in China,No.Y20120154(to ZZ) and Y20140686(to ZH)the Projects of International Cooperation and Exchanges National Natural Science Foundation of China,No.81620108011(to XMJ)
文摘We previously demonstrated that administering 2-（2-benzofuranyl）-2-imidazolin（2-BFI）, an imidazoline I2 receptor agonist, immediately after ischemia onset can protect the brain from ischemic insult. However, immediate administration after stroke is difficult to realize in the clinic. Thus, the therapeutic time window of 2-BFI should be determined. Sprague-Dawley rats provided by Wenzhou Medical University in China received right middle cerebral artery occlusion for 120 minutes, and were treated with 2-BFI（3 mg/kg） through the caudal vein at 0, 1, 3, 5, 7, and 9 hours after reperfusion. Neurological function was assessed using the Longa＇s method. Infarct volume was measured by 2,3,5-triphenyltetrazolium chloride assay. Morphological changes in the cortical penumbra were observed by hematoxylin-eosin staining under transmission electron microscopy. The apoptosis levels in the ipsilateral cortex were examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling（TUNEL） assay. The protein expression of Bcl-2 and BAX was detected using immunohistochemistry. We found the following： Treatment with 2-BFI within 5 hours after reperfusion obviously improved neurological function. Administering 2-BFI within 9 hours after ischemia/reperfusion decreased infarct volume and alleviated apoptosis. 2-BFI administration at different time points after reperfusion alleviated the pathological damage of the ischemic penumbra and reduced the number of apoptotic neurons, but the protective effect was more obvious when administered within 5 hours. Administration of 2-BFI within 5 hours after reperfusion remarkably increased Bcl-2 expression and decreased BAX expression. To conclude, 2-BFI shows potent neuroprotective effects when administered within 5 hours after reperfusion, seemingly by up-regulating Bcl-2 and down-regulating BAX expression. The time window provided clinical potential for ischemic stroke by 2-BFI.
基金supported by the National Natural Science Foundation of China (No.21473167 and No.21688102)the National Key Research and Development Program of China (No.2016YFA0200604)+1 种基金the Fundamental Research Funds for the Central Universities (WK3430000005,WK2340000065)the China Scholarship Council (CSC) (No.201706345015)
文摘Based on density functional theory calculations,the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene(Pt1/Gr-O)is investigated.It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B-H bonds breaking.Then one H2O molecule attacks the left*BHNH3 group(*represents adsorbed state)to form*BH(H2O)NH3 and the elongated O-H bond is easily broken to produce*BH(OH)NH3.The second H2O molecule attacks*BH(OH)NH3 to form*BH(OH)(H2O)NH3 and the breaking of O-H bond pointing to the plane of Pt1/Gr-O results in the desorption of BH(OH)2NH3.The second hydrogen molecule is produced from two hydrogen atoms coming from two H2O molecules and Pt1/Gr-O is recovered after the releasing of hydrogen molecule.The third hydrogen molecule is generated by the further hydrolysis of BH(OH)2NH3 in water solution.The rate-limiting step of the whole process is the combination of one H2O molecule and*BHNH3 with an energy barrier of 16.1 kcal/mol.Thus,Pt1/Gr-O is suggested to be a promising catalyst for hydrolysis of NH3BH3 at room temperature.
文摘Using first-principles calculations, we studied the interaction of methanol with the Pt（100） surface based on generalized gradient approximation. We found that top sites of Pt（100） surface are the favored adsorptive positions in energy, and methanol molecule interacts with the Pt surface through oxygen atoms. Moreover, we also explored the possible dissociation pathways of methanol on the Pt surface, and suggested that the products of dissociation can be controlled by the external manipulation.
基金supported by the National Natural Science Foundation of China (No.21688102,No.21803066,and No.22003061)the Chinese Academy of Sciences Pioneer Hundred Talents Program (KJ2340000031,KJ2340007002)+7 种基金the National Key Research and Development Program of China(2016YFA0200604)the Anhui Initiative in Quantum Information Technologies (AHY090400)the Strategic Priority Research of Chinese Academy of Sciences(XDC01040100)CAS Project for Young Scientists in Basic Research (YSBR-005)the Fundamental Research Funds for the Central Universities (WK2340000091,WK2060000018)the Hefei National Laboratory for Physical Sciences at the Microscale (SK2340002001)the Research Start-Up Grants (KY2340000094)the Academic Leading Talents Training Program(KY2340000103) from University of Science and Technology of China
文摘KSSOLV(Kohn-Sham Solver)is a MATLAB(Matrix Laboratory)toolbox for solving the Kohn-Sham density functional theory(KS-DFT)with the plane-wave basis set.In the KS-DFT calculations,the most expensive part is commonly the diagonalization of Kohn-Sham Hamiltonian in the self-consistent field(SCF)scheme.To enable a personal computer to perform medium-sized KS-DFT calculations that contain hundreds of atoms,we present a hybrid CPU-GPU implementation to accelerate the iterative diagonalization algorithms implemented in KSSOLV by using the MATLAB built-in Parallel Computing Toolbox.We compare the performance of KSSOLV-GPU on three types of GPU,including RTX3090,V100,and A100,with conventional CPU implementation of KSSOLV respectively and numerical results demonstrate that hybrid CPU-GPU implementation can achieve a speedup of about 10 times compared with sequential CPU calculations for bulk silicon systems containing up to 128 atoms.
基金the National Key Basic Research Program，the National Natural Science Foundation of China，the Chinese Academy of Sciences，USTCSCC, SCCAS, Tianjin, and Shanghai Supercomputer Centers
基金Ⅴ. ACKNOWLEDGMENTS This work was partially supported by the National Natural Science Foundation of China （No.50721091, No.20533030, No.50731160010, No.20873129, and No.20803071）, the National Key Basic Research Program （No.2006CB922004）, the USTC-HP HPC Project, and by the SCCAS and Shanghai Supercomputer Center.
文摘FeAs^- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation （GGA） and GGA＋U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs^- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that, in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.
基金Ⅴ. ACKN0WLEDGEMENTS This work was supported by the National Project for the Development of Key Fhndamental Sciences in China （G1999075305）, the National Natural Science Foundation of China （50121202, 10474087）, the USTCHP HPC project, and the SCCAS.
文摘The geometrical and electronic properties of the anionic and neutral V2O6 clusters were studied with the spin unrestricted hybrid density functional B3LYP method. The calculated ground states of both clusters are different from the previous theoretical results. The ground state of V2O6^- is found to be a doublet with C2v symmetry, while a doublet with D2h symmetry was previously obtained by Vyboishchikov and Sauer. For neutral V206, the ground state is an open-shell singlet with D2h symmetry whose energy is very close to that of the triplet state. In contrast, a closed-shell singlet with D2h symmetry was obtained by Vyboishchikov and Sauer, and Calatayud et al. found a triplet ground state with Cs symmetry. Moreover, the calculated adiabatic and vertical detachment energies of the anion cluster are in much better agreement with the experimental results of photoelectron spectroscopy than previous theoretical values.
文摘To the Editor:Autonomic dysfunction is an important factor in the pathogenesis of unstable angina pectoris (UAP).It affects coronary artery systolic function,induces coronary spasm,aggravates myocardial ischemia,reduces ventricular fibrillation threshold,and increases the incidence of sudden cardiac death in UAP.
基金supported by China Postdoctoral Science Foundation(Nos.2013M530618 and 2015M572136)National Natural Science Foundation of China(Nos.51172120 and 51372093)+2 种基金Fundamental Research Funds for the Central Universities(HUST:2015J07)Open Fund of State Key Laboratory of New Ceramic and Fine Processing(Tsinghua University)(No.KF201518)the 02 Important and Special Project for the State Science and Technology(No.2013ZX2104-001-002).
文摘Porous Si_(3)N_(4) ceramics were prepared by aqueous gelcasting using Si_(3)N_(4) poly-hollow microspheres(PHMs)as pore-forming agent.The effects of solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content on the properties of porous Si_(3)N_(4) ceramics were investigated.Onlyβ-Si_(3)N_(4) phase is observed in porous Si_(3)N_(4) ceramics,and Si_(3)N_(4) PHMs distribute uniformly both in Si_(3)N_(4) green samples and porous Si_(3)N_(4) ceramics.Results show that solid loading of Si_(3)N_(4) slurry and Si_(3)N_(4) PHM content could considerably influence the properties of porous Si_(3)N_(4) ceramics.With the increase of solid loading of Si_(3)N_(4) slurry(decrease of Si_(3)N_(4) PHM content),the distributing state of Si_(3)N_(4) PHMs changes from contacting with each other to just embedding in the matrix,thus their porosity decreases,while their shrinkage,flexural strength,and fracture toughness increase.
基金supported by the National Natural Science Foundation of China(No.21603026)Sichuan Science and Technology Program(No.2018RZ0115).
文摘Polymer microspheres with uniform size,composition,and surface property have gained extensive researches in past decades.Conventional bottom-up approaches are using monomers or oligomers to build up desired polymer microspheres.However,directly shaping high-molecular-weight polymers into well-ordered polymer microspheres remains a great challenge.Herein,we reported a facile and efficient top-down approach tofabricate microspheres with high-molecular-weight polymer microfibers.By harnessing interfacial engineering-control during the polymer microspheres formation,uniformly sized microspheres could be produced with widely ranged diameters(from 10μm to the capillary length of each polymer melt).The size limitation of this approach could be further extended by a controllable Plateau-Rayleigh instability phenomenon.Principally,the top-down approach allows fabrication of microspheres by various polymer melts with surface energy higher than 25 mN/m.Our work paves a way for green,cost-effective,and customizable production of a variety of functional polymer microspheres without any chemical reaction assistant.
基金Our research work presented in this paper was supported by China Postdoctoral Science Foundation，Fundamental Research Funds for the Central Universities，Open Project of State Key Laboratory of New Ceramics and Fine Processing of Tsinghua University，Basic Research Project of Shenzhen
文摘In this paper, novel Al2O3-based poly-hollow microsphere (PHM) ceramics were prepared using Si3N4 and Al2O3 PHMs as pore-forming agents. The effect of Si3N4 and Al2O3 PHMs with different percentages on properties of Al2O3-based PHM ceramics was investigated. Through adjusting percentage of Al2O3 PHMs, Al2O3-based PHM ceramics with enhanced properties are achieved. X-ray diffraction (XRD) results show that main phases of Al2O3-based PHM ceramics vary from beta-SiAlON (z value increases from 2.9 to 4) to Al2O3 with the increase of percentage of Al2O3 PHMs from 10% to 100%. The different phase compositions result in different properties of Al2O3-based PHM ceramics. With the increase of percentage of Al2O3 PHMs, porosity of Al2O3-based PHM ceramics gradually decreases, while their shrinkage, flexural strength, and fracture toughness firstly decrease and then increase. Using different kinds of ceramic PHMs as pore-forming agents, various novel and high-performance porous ceramics could be prepared via optimizing percentage of ceramic PHMs in the future.
