ABSTRACT
Isothermal hot compression experiments were conducted on Mg-2.5Nd-0.5Zn-0.5Zr alloy to investigate hot deformation behavior at the temperature range of 573-773 K and the strain rate range of 0.001 s-1-10 s-1 using a Gleeble-3500D thermomechanical simulator. The results showed that the rheological curve showed a typical work hardening stage, and there were three different stages: work hardening, transition and steady state. A strain compensation constitutive model was established to predict the flow stress of the Mg-2.5Nd-0.5Zn-0.5Zr alloy, and the results proved that it had high predictability. The main deformation mechanism of the Mg-2.5Nd-0.5Zn-0.5Zr alloy was dislocation climbing. The processing maps were established to distinguish the unstable region from the working region. The maps showed that the instability generally occurred at high strain rates and low temperatures, and the common forms of instability were cracking and flow localization. The optimum machining range of the alloy was determined to be 592-773 K and 0.001-0.217 s-1. With the increase in deformation temperature, the grain size of the alloy grew slowly at the 573-673 K temperature range and rapidly at the 673-773 K temperature range.
ABSTRACT
Hot stamping is a well-known process to produce structural automotive parts with an excellent strength-to-weight ratio. However, this process is more expensive due to the lower energy efficiency and operating cost of the traditional roller-hearth furnace. Additionally, lower ductility and toughness are commonly recognized as the main disadvantages of the current hot stamped ultra-high-strength parts. Refinement of austenite grains could be a profitable way to improve the strength of hot stamped parts. In this work, the evolution of reversed transformation in asymmetrically cryogenically rolled samples was studied in order to control the austenite. Thermomechanical simulation and heat treatment in the salt bath were used to investigate the reversed transformation process, and the typical microstructures were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Compared with symmetric prerolling, ferrite recrystallization could be remarkably inhibited by asymmetric rolling at the liquid nitrogen temperature (LNT) during the reheating process. Additionally, the nucleation of the austenite inner grains can also be promoted and the dynamics of the reversed transformation accelerated by asymmetric prerolling. Such phenomena might be very useful to refine the parent austenite grains before press hardening and enhance the new hot stamping strategy by partial fast reheating.
ABSTRACT
Half smooth tongue sole, Cynoglossus semilaevis (Pleuronectiformes, Cynoglossidae), is an important aquaculture species throughout coastal areas of China which has a high nutritional and economic value. Genetic linkage map is an important tool for accelerating aquatic breeding process through marker assisted selection (MAS) and quantitative trait locus (QTL). Here, 325 polymorphic microsatellite markers were explored and sex-specific genetic linkage map were constructed using these markers. The female map contained 193 markers located at 21 linkage groups, with a total length of 1041cM and an average resolution of 6.8cM; the male map contained 195 markers located at 21 linkage groups, with a total length of 1154cM and an average resolution of 7.2cM, they covered approximately 76.72% and 78.12% genomes, respectively. The recombination ratio of female/male was about 1:1.02 estimated in the sex-specific frame map. All developed microsatellite markers and this linkage map could serve as the foundation for further study in high density linkage map construction.
Subject(s)
Flatfishes/genetics , Genetic Linkage , Microsatellite Repeats/genetics , Animals , Chromosome Mapping , Female , Genotype , Male , Sex FactorsABSTRACT
Hepcidin, an antimicrobial peptide, has a dual function including innate immunity and iron regulation. Here, based on the sequence of an EST database, we have isolated and characterized a hepcidin gene (referred to as CsHepcidin) from half-smooth tongue sole (Cynoglossus semilaevis). Analysis of the coding regions indicated CsHepcidin gene comprised 3 exons and 2 introns. The putative CsHepcidin showed a great similarity to other hepcidin orthologues, particularly with respect to its 24 aa signal peptide, typical RX(K/R)R motif and eight conserved cysteine residues in the mature cationic peptide. Phylogenic analysis indicated that CsHepcidin was a hepcidin 1-type peptide of acanthopterygians, with highly homologous with Solea senegalensis hepcidin. In C. semilaevis ontogeny, CsHepcidin mRNA was detected at a low level in unfertilized eggs, increased on 6 d after hatching, and decreased remarkably at metamorphic stage. CsHepcidin transcripts showed a constitutive basal expression in most of the tissues, especially in liver. Challenge with formalin-inactivated Vibrio anguillarum led to significantly up-regulations of CsHepcidin gene in liver, head kidney and spleen in time-dependent manners. Biological activity analysis showed that recombinant CsHEP exhibited direct antimicrobial activity against bacterial pathogens in vitro, particularly showed strong activity against the principal fish pathogens, V. anguillarum and Edwardsiella tarda. All these results suggest that CsHepcidin may be involved in the initial response to invasion of microbial pathogens. Further exploration to elucidate the role of CsHepcidin in iron regulation and embryogenesis in C. semilaevis are needed.
