The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H...The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.展开更多
The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces...The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces. In the present study, the authors constructed five variants of Ps3aHSD （Pseudomonas sp. B-0831 3a-hydroxysteroid dehydrogenase） in which one or two residues at the dimer interface were replaced with aromatic residues, and examined the effects of introducing aromatic residues in this region on protein thermostability. Under their experimental conditions, all variants formed dimers, similar to wild-type Ps3aHSD. Thermal denaturation experiments indicated that Tm of all variants was 0.2-16.2 °C lower than that of wild-type protein, indicating less stable thanwild-type protein. The results collectively suggest that aromatic residues of natural oligomeric proteins are strictly posted in the interface to facilitate optimal interactions and avoid conformational strain.展开更多
A solute trapping model is developed based on a so-called solute drag treatment.By adopting a basic approach of phase-field models,and defining the free energy density in the interfacial region,a suitable interface sh...A solute trapping model is developed based on a so-called solute drag treatment.By adopting a basic approach of phase-field models,and defining the free energy density in the interfacial region,a suitable interface shape function is introduced to derive the current model,in which the equilibrium and non-equilibrium interface behaviours can be described using a dimensionless parameter L (i.e.an important parameter in the present interface shape function).When applying the current model to Si-9%As (molar fraction) alloy with L=0.5,a good prediction of the steeper profile for high interface velocity,which is analogous to that using a phase-field model of DANILOV and NESLTER,has been obtained.展开更多
基金Project(2011KJZD04)supported by the CHINALCO Science and Development Foundation,China
文摘The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.
文摘The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces. In the present study, the authors constructed five variants of Ps3aHSD （Pseudomonas sp. B-0831 3a-hydroxysteroid dehydrogenase） in which one or two residues at the dimer interface were replaced with aromatic residues, and examined the effects of introducing aromatic residues in this region on protein thermostability. Under their experimental conditions, all variants formed dimers, similar to wild-type Ps3aHSD. Thermal denaturation experiments indicated that Tm of all variants was 0.2-16.2 °C lower than that of wild-type protein, indicating less stable thanwild-type protein. The results collectively suggest that aromatic residues of natural oligomeric proteins are strictly posted in the interface to facilitate optimal interactions and avoid conformational strain.
基金Projects(50501020, 50395103, 50431030) supported by the National Natural Science Foundation of China Project(NCET-05-870) supported by Program for New Century Excellent Talents in University of China Project(CX200706) supported by the Doctorate Foundation of Northwestern Polytechnical University,China
文摘A solute trapping model is developed based on a so-called solute drag treatment.By adopting a basic approach of phase-field models,and defining the free energy density in the interfacial region,a suitable interface shape function is introduced to derive the current model,in which the equilibrium and non-equilibrium interface behaviours can be described using a dimensionless parameter L (i.e.an important parameter in the present interface shape function).When applying the current model to Si-9%As (molar fraction) alloy with L=0.5,a good prediction of the steeper profile for high interface velocity,which is analogous to that using a phase-field model of DANILOV and NESLTER,has been obtained.
