Cloning the Structure Genes and Expression the N Gene of Porcine Epidemic Diarrhea Virus DX

The structure genes spike(S) ,nucleocapsid(N) ,membrane(M) ,small membrane(sM) of a porcine epidemic diarrhea virus(PEDV) strain DX isolated in Gansu province,North-west of China,were cloned,sequenced and compared with published sequences of PEDV strains. The nucleotide sequences encoding the entire S,sM,M and N genes open reading frame(ORF) of DX were 4 152,231,681 and 1 326 bases long respectively. There were transcription regulatory sequences(TRSs) upstream of the initiator ATG of the S,N and M genes. The amino acids sequences of S,M and N contained 30,3 and 7 potential asparagine(N) -linked glycosylation sites. Homologous analysis and phylogenetic trees showed that DX had the closest relationship with strains LJB/06,JS-2004-2Z and CH/HLJH/06 that were also isolated from China and indicated the prevalence of some PEDV isolates in China were widespread since the JS-2004-2Z strain originated from the south of the China,and LJB/06 and CH/HLJH/06 were isolated from northeast China. The N gene was cloned using two primers which contained Nco I and BamH I restriction enzyme sites and subcloned into expression vector pET30a. The recombinant plasmid was then transformed into E.coli Rossta. SDS-PAGE showed there was a protein of about 55kDa as expected and Western blot indicated the N protein had biological activity.

Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction （RD） and normal direction （ND） of sheets （dr/dn）. A mathematical model （ r = e^0.345（dn^1/2-dr^1/2） ） was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production （CSP）. It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.

Effect of hot rolling on the microstructure and impact absorbed energy of the strip steel by CSP

The microstructures and impact absorbed energies at various temperatures were investigated for steel strips hot rolled to thickness reductions of 95.5%, 96.0%, 96.5%, 97.0%, and 97.5%. Results indicate that grain refinement can be realized with an increase in hot rolling reduction. Besides, finer precipitates can be achieved with an increase in hot rolling reduction from 95.5%to 97.0%. The impact absorbed energy decreases with a decrease in testing temperature for steel strips hot rolled to 95.5%, 96.0%, and 96.5%reductions in thickness. However, in the case of steel strips hot rolled to 97.0%and 97.5%reductions in thickness, the impact absorbed energy remained almost constant with a decrease in testing temperature.

Effect of nano-sized precipitates on the crystallography of ferrite in high-strength strip steel

For strip steel with the thickness of 1.6 ram, the yield and tensile strengths as high as 760 and 850 MPa, respectively, were achieved using the compact strip production technology. Precipitates in the steel were characterized by scanning and transmission electron microscopy to elucidate the strengthening mechanism. In addition, intragranular misorientation, Kernel average misorientafion, and stored energy were measured using electron backscatter diffraction for crystallographic analysis of ferrite grains containing precipitates and their neighbors without precipitates. It is found that precipitates in specimens primarily consist of TiC and Ti4CzS2. Ferrite grains containing pre- cipitates exhibit the high Taylor factor as well as the crystallographic orientations with {012}, {011}, {112}, or {221} plane parallel to the rolling plane. Compared with the intragranular orientation of adjoining grains, the intragranular misorientation of grains containing precipi- tates fluctuates more frequently and more mildly as a function of distance. Moreover, the precipitates can induce ferrite grains to store a rela- tively large amount of energy. These results suggest that a correlation exists between precipitation in ferrite grains and grain crystallographic properties.