This study aims to investigate the promotion effect of twinning-induced nucleation vs the inhibition effect of Mgi7Ali2 particles pinning for recrystallization, achieved through gradient rolling for Mg-3Al-lZn (AZ31) ...This study aims to investigate the promotion effect of twinning-induced nucleation vs the inhibition effect of Mgi7Ali2 particles pinning for recrystallization, achieved through gradient rolling for Mg-3Al-lZn (AZ31) and Mg-9Al-lZn (AZ91) alloys as well as pure Mg. Through gradient rolling, a transition zone from the initial to deformed microstructure undergoing varying thickness reductions was obtained in the same sample, where the evolution of deformation twins and second phase can be examined precisely and continuously. During hot deformation, dynamic recrystallized (DRXed) grains tended to originate from {10 T 1 }-{10 T 2} double twins, whose nucleation was significantly restricted by increasing A1 content and hence recrystallization can be rarely triggered in AZ91 alloy. Concurrently, the size and volume fraction of Mgi7Ali2 particles changed via dissolution and re-precipitation, leading to finer average size and higher volume fraction, which produced stronger pinning effect and hindered dynamic recrystallization significantly. The current study provides insights into the mechanisms responsible for dynamic recrystallization behavior during hot rolling in Mg-AI-Zn alloys.展开更多
Commercial wrought Mg alloys normally contain low alloying contents to ensure good formability.In the present work,high-alloyed Mg-6 Al-4 Zn-x Sn(x=1,2 and 3 wt.%,respectively)alloys were fabricated by extrusion.Herei...Commercial wrought Mg alloys normally contain low alloying contents to ensure good formability.In the present work,high-alloyed Mg-6 Al-4 Zn-x Sn(x=1,2 and 3 wt.%,respectively)alloys were fabricated by extrusion.Hereinto,Sn was proven to play an effective contribution to simultaneous improvement in strength and ductility that are traditional trade-off features of synthetic materials.It was found that the average grain size of those alloys decreases significantly from^11 to^4μm as a function of Sn contents increasing from 0 to 3 wt.%,while the amounts of Mg2 Sn and Mg17 Al12 particles continuously increase.More importantly,the addition of Sn leads to the transformation of dominated deformation modes from{1012}extension twinning(1 wt.%)to pyramidal slip(3 wt.%)during tensile tests along the extrusion direction at room temperature.The advantageous combination of ultimate tensile strength(~366 MPa)and elongation(~19%)in Mg-6Al-4Zn-3 Sn alloy is mainly attributed to the strong strain hardening ability induced by the enhanced activity of non-basal slip.This work could provide new opportunities for the development of high-alloyed wrought Mg alloys with promising mechanical properties.展开更多
Proteolysis is one of the most important biochemical reactions during cheese ripening.Studies on the secondary structure of proteins during ripening would be helpful for characterizing protein changes for assessing ch...Proteolysis is one of the most important biochemical reactions during cheese ripening.Studies on the secondary structure of proteins during ripening would be helpful for characterizing protein changes for assessing cheese quality.Fourier transform infrared spectroscopy(FTIR),with self-deconvolution,second derivative analysis and band curve-fitting,was used to characterize the secondary structure of proteins in Cheddar cheese during ripening.The spectra of the amide I region showed great similarity,while the relative contents of the secondary structures underwent a series of changes.As ripening progressed,the α-helix content decreased and the β-sheet content increased.This structural shift was attributed to the strengthening of hydrogen bonds that resulted from hydrolysis of caseins.In summary,FTIR could provide the basis for rapid characterization of cheese that is undergoing ripening.展开更多
The preparation of ordered porous metal oxide films by anodic oxidation is an efficient and simple preparation method.However,there has been no unified explanation about the formation mechanism of the porous structure...The preparation of ordered porous metal oxide films by anodic oxidation is an efficient and simple preparation method.However,there has been no unified explanation about the formation mechanism of the porous structure for many years.In this paper,the relationship between the crystal structure of metals and the morphology of ordered porous metal oxide films is proposed.The influence of the crystal structures of different metals on the optimal morphology of porous films is discussed.展开更多
Al-Mg-Si(AA6xxx)series alloys have been used widely in automotive industry for lightweight purpose.This work focuses on developing a short process for manufacturing Al-0.5Mg-1.3Si(wt.%)alloy sheets with good mechanica...Al-Mg-Si(AA6xxx)series alloys have been used widely in automotive industry for lightweight purpose.This work focuses on developing a short process for manufacturing Al-0.5Mg-1.3Si(wt.%)alloy sheets with good mechanical properties.Hereinto,a preparation route without homogenization was proposed on the basis of sub-rapid solidification(SRS)technique.The sample under SRS has fine microstructure and higher average partition coefficients of solute atoms,leading to weaker microsegregation owing to the higher cooling rate(160℃/s)than conventional solidification(CS,30℃/s).Besides,Mg atoms tend to be trapped in Al matrix under SRS,inducing suppression of Mg2Si,and promoting generation of Al Fe Si phase.After being solution heat treated(T4 state),samples following the SRS route have lower yield strength compared with that by CS route,indicating better formability in SRS sample.After undergoing pre-strain and artificial aging(T6 state),the SRS samples have comparable yield strength to CS samples,satisfying the service requirements.This work provides technological support to industrially manufacture high performance AA6xxx series alloys with competitive advantage by a novel,short and low-cost process,and open a door for the further development of twin-roll casting based on SRS technique in industries.展开更多
A new route for the synthesis of DW286, 7-[3-（aminomethyl）-4-（methoxyimino）-3-methyltetrahy- dro-1H-1-pyrrolyl]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid hydrochloric acid salt, ...A new route for the synthesis of DW286, 7-[3-（aminomethyl）-4-（methoxyimino）-3-methyltetrahy- dro-1H-1-pyrrolyl]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid hydrochloric acid salt, is described. In the presence of benzadehyde, DW286 was prepared by the direct condensation of 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid with new pyrrolidine derivative 7 which could be obtained by routine reactions.展开更多
A series of novel moxifloxacin methylene and ethylene isatin derivatives with remarkable improvement in lipophilicity, compared to the parent moxifloxacin, was designed, synthesized and characterized by 1H NMR, MS and...A series of novel moxifloxacin methylene and ethylene isatin derivatives with remarkable improvement in lipophilicity, compared to the parent moxifloxacin, was designed, synthesized and characterized by 1H NMR, MS and HRMS. These derivatives were initially evaluated for their in vitro antimycobacterial activity against M. smegmatis CMCC 93202. Compounds 3a―3f, 5a, 5f and 5j were chosen for the further evaluation of their in vitro activity against Mycobacterium tuberculosis（MTB） H37Rv ATCC 27294 and MDR-MTB 09710. All the target com pounds[minimum inhibitory concentration（MIC）： 0.39―〉16 μg/mL] were far more active than rifampin（MIC： 2.0―〉256 μg/mL）, but less active than moxifloxacin（MIC： 0.1―1.0 μg/mL） against the three tested strains. The most active compounds 3a and 3c were found to be 2―64 fold more potent than isoniazid and rifampin against M. smegmatis CMCC 93202, 2 fold more potent than rifampin against MTB H37Rv ATCC 27294, and 16―〉64 fold more potent than ethambutol, isoniazid and rifampin against MDR-MTB 09710.展开更多
基金financially supported by the National Key Research and Development Program (Nos. 2017YFA0403700 and 2016YFE0115300)the National Natural Science Foundation of China (Nos. 51671093, 51625402, and 51790483)Partial financial support came from The Changjiang Scholars Program (No. T2017035)
文摘This study aims to investigate the promotion effect of twinning-induced nucleation vs the inhibition effect of Mgi7Ali2 particles pinning for recrystallization, achieved through gradient rolling for Mg-3Al-lZn (AZ31) and Mg-9Al-lZn (AZ91) alloys as well as pure Mg. Through gradient rolling, a transition zone from the initial to deformed microstructure undergoing varying thickness reductions was obtained in the same sample, where the evolution of deformation twins and second phase can be examined precisely and continuously. During hot deformation, dynamic recrystallized (DRXed) grains tended to originate from {10 T 1 }-{10 T 2} double twins, whose nucleation was significantly restricted by increasing A1 content and hence recrystallization can be rarely triggered in AZ91 alloy. Concurrently, the size and volume fraction of Mgi7Ali2 particles changed via dissolution and re-precipitation, leading to finer average size and higher volume fraction, which produced stronger pinning effect and hindered dynamic recrystallization significantly. The current study provides insights into the mechanisms responsible for dynamic recrystallization behavior during hot rolling in Mg-AI-Zn alloys.
基金the National Key Research and Development Program(No.2016YFE0115300)the National Natural Science Foundation of China(Nos.51625402,51790483,and 51801069)+1 种基金Partial financial supports come from the Science and Technology Development program of Jilin Province(Nos.JJKH20180129KJ and 20190103003JH)The Changjiang Scholars Program(T2017035)。
文摘Commercial wrought Mg alloys normally contain low alloying contents to ensure good formability.In the present work,high-alloyed Mg-6 Al-4 Zn-x Sn(x=1,2 and 3 wt.%,respectively)alloys were fabricated by extrusion.Hereinto,Sn was proven to play an effective contribution to simultaneous improvement in strength and ductility that are traditional trade-off features of synthetic materials.It was found that the average grain size of those alloys decreases significantly from^11 to^4μm as a function of Sn contents increasing from 0 to 3 wt.%,while the amounts of Mg2 Sn and Mg17 Al12 particles continuously increase.More importantly,the addition of Sn leads to the transformation of dominated deformation modes from{1012}extension twinning(1 wt.%)to pyramidal slip(3 wt.%)during tensile tests along the extrusion direction at room temperature.The advantageous combination of ultimate tensile strength(~366 MPa)and elongation(~19%)in Mg-6Al-4Zn-3 Sn alloy is mainly attributed to the strong strain hardening ability induced by the enhanced activity of non-basal slip.This work could provide new opportunities for the development of high-alloyed wrought Mg alloys with promising mechanical properties.
基金financially supported by Beijing Municipal Commission of Education Co-Constructed Programand Chinese Universities Scientific Fund(2009-4-25)
文摘Proteolysis is one of the most important biochemical reactions during cheese ripening.Studies on the secondary structure of proteins during ripening would be helpful for characterizing protein changes for assessing cheese quality.Fourier transform infrared spectroscopy(FTIR),with self-deconvolution,second derivative analysis and band curve-fitting,was used to characterize the secondary structure of proteins in Cheddar cheese during ripening.The spectra of the amide I region showed great similarity,while the relative contents of the secondary structures underwent a series of changes.As ripening progressed,the α-helix content decreased and the β-sheet content increased.This structural shift was attributed to the strengthening of hydrogen bonds that resulted from hydrolysis of caseins.In summary,FTIR could provide the basis for rapid characterization of cheese that is undergoing ripening.
基金financially supported by the National Key Research and Development program of China(Nos.2021YFA1401103 and 2016YFA0202703)the National Natural Science Foundation of China(Nos.61825403,61921005 and 61674078)+1 种基金the Natural Science Foundation of Hebei Province(No.A2020205038)the Postgraduate Demonstration Course Project of Hebei Province(No.KCJSX2021038)。
文摘The preparation of ordered porous metal oxide films by anodic oxidation is an efficient and simple preparation method.However,there has been no unified explanation about the formation mechanism of the porous structure for many years.In this paper,the relationship between the crystal structure of metals and the morphology of ordered porous metal oxide films is proposed.The influence of the crystal structures of different metals on the optimal morphology of porous films is discussed.
基金Financial supports from The National key research and development program(No.2016YFE0115300)The Natural Science Foundation of China(Nos.51790483,51625402,51790485 and 51801069)are greatly acknowledged+2 种基金Partial financial support came from The science and technology development program of Jilin Province(No.20190901010JC)The Changjiang Scholars Program(T2017035)the Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09).
文摘Al-Mg-Si(AA6xxx)series alloys have been used widely in automotive industry for lightweight purpose.This work focuses on developing a short process for manufacturing Al-0.5Mg-1.3Si(wt.%)alloy sheets with good mechanical properties.Hereinto,a preparation route without homogenization was proposed on the basis of sub-rapid solidification(SRS)technique.The sample under SRS has fine microstructure and higher average partition coefficients of solute atoms,leading to weaker microsegregation owing to the higher cooling rate(160℃/s)than conventional solidification(CS,30℃/s).Besides,Mg atoms tend to be trapped in Al matrix under SRS,inducing suppression of Mg2Si,and promoting generation of Al Fe Si phase.After being solution heat treated(T4 state),samples following the SRS route have lower yield strength compared with that by CS route,indicating better formability in SRS sample.After undergoing pre-strain and artificial aging(T6 state),the SRS samples have comparable yield strength to CS samples,satisfying the service requirements.This work provides technological support to industrially manufacture high performance AA6xxx series alloys with competitive advantage by a novel,short and low-cost process,and open a door for the further development of twin-roll casting based on SRS technique in industries.
基金Supported by the National S&T Major Special Project of China on Major New Drug Innovation(No.2009ZX09301-003)
文摘A new route for the synthesis of DW286, 7-[3-（aminomethyl）-4-（methoxyimino）-3-methyltetrahy- dro-1H-1-pyrrolyl]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid hydrochloric acid salt, is described. In the presence of benzadehyde, DW286 was prepared by the direct condensation of 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid with new pyrrolidine derivative 7 which could be obtained by routine reactions.
基金Supported by the National Key Project of Major Infectious Disease of China(No.2008ZX10003-006)the National S&T Major Special Project on Major New Drug Innovation, China(No.2009ZX09301-003)
文摘A series of novel moxifloxacin methylene and ethylene isatin derivatives with remarkable improvement in lipophilicity, compared to the parent moxifloxacin, was designed, synthesized and characterized by 1H NMR, MS and HRMS. These derivatives were initially evaluated for their in vitro antimycobacterial activity against M. smegmatis CMCC 93202. Compounds 3a―3f, 5a, 5f and 5j were chosen for the further evaluation of their in vitro activity against Mycobacterium tuberculosis（MTB） H37Rv ATCC 27294 and MDR-MTB 09710. All the target com pounds[minimum inhibitory concentration（MIC）： 0.39―〉16 μg/mL] were far more active than rifampin（MIC： 2.0―〉256 μg/mL）, but less active than moxifloxacin（MIC： 0.1―1.0 μg/mL） against the three tested strains. The most active compounds 3a and 3c were found to be 2―64 fold more potent than isoniazid and rifampin against M. smegmatis CMCC 93202, 2 fold more potent than rifampin against MTB H37Rv ATCC 27294, and 16―〉64 fold more potent than ethambutol, isoniazid and rifampin against MDR-MTB 09710.
