Effects of Electric and Magnetic Treatments on Microstructures of Solid Metals: A Review

An external electric or magnetic field can transfer high-intensity energy directly to the electronic scale of materials,and change the spin,energy level arrangement and trajectory of electrons.These changes produce tremendous and profound impacts on the microstructure and mechanical properties of metal materials,which may be impos-sible with traditional technologies.This paper reviews the effects of electric or magnetic field on the microstruc-tures of solid metals including phase transformation,precipitation,recrystallization,dislocations and so on.Based on the existing research results,the mechanisms of these effects have been discussed.Additionally,some typical applications of electric and magnetic treatments on solid metals have been described and the challenges in this field have also been discussed.

Characterization of DNA polymerase δ from deep-sea hydrothermal vent shrimp Rimicaris exoculata

DNA polymerase δ(Polδ)plays a crucial and versatile role in DNA replication and DNA repair processes.Vent shrimp Rimicaris exoculata is the primary megafaunal community living in hydrothermal vents.In this study,the Polδfrom shrimp Rimicaris exoculata was cloned,expressed and characterized.The results showed that the Polδcatalytic subunit(POLD1),852 amino acids in length,shared high homology with crayfish Procambarus clarkii and shrimp Oratosquilla oratoria.The recombinant POLD1 expressed in Escherichia coli showed that the enzyme was active in a range of 20℃ to 40℃ with an optimum temperature at 25℃ and in a wide range of p H with an optimum at pH 6.0.The activities of POLD1 were significantly enhanced in the presence of Triton-X 100,Tween 20 and Mn^(2+).The K_(m)(dNTP)value of POLD1 was 4.7μmol/L.The present study would be helpful to reveal the characterization of Polδof deep-sea vent animals.

Ozone-Mediated Functionalization of Multi-Walled Carbon Nanotubes and Their Activities for Oxygen Reduction Reaction

The functionalization of multi-walled carbon nanotubes(MWCNTs)by ozone treatment has been systematically investigated by using Raman spectroscopy,transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),organic elemental analysis(OEA)and Boehm titration.The results showed that the functionalization process occurred at defective sites(opened mouths,tube caps,debris,etc.)before opening caps and truncating walls,and finally the graphitic structure was deteriorated.The surface oxygen content first increased with the treatment time but kept at around 8.0 wt%after 5 h.The analysis of the distribution of oxygen-containing groups revealed that phenolic hydroxyl was gradually converted to carboxyl and lactone.The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the catalyst for oxygen reduction reaction(ORR).