Influence of rheo-diecasting processing parameters on microstructure and mechanical properties of hypereutectic Al-30%Si alloy

The effects of pouring temperature,vibration frequency,and the number of curves in a serpentine channel,on themicrostructure and mechanical properties of Al-30%Si alloy processed by rheo-diecasting(RDC)were investigated.The semisolidAl-30%Si alloy slurry was prepared by vibration serpentine channel pouring(VSCP)process in the RDC process.The results showthat the pouring temperature,the vibration frequency,and the number of the curves strongly affect the microstructure and mechanicalproperties of Al-30%Si alloy.Under experimental conditions of a pouring temperature of850°C,a twelve-curve copper channel anda vibration frequency of80Hz,the primary Si grains are refined into fine compact grains with average grain size of about24.6μm inthe RDC samples assisted with VSCP.Moreover,the ultimate tensile strength(UTS),elongation and hardness of the RDC sample are296MPa,0.87%and HB155,respectively.It is concluded that the VSCP process can effectively refine the primary Si grains.Therefinement of primary Si grains is the major cause for the improvement of the mechanical properties of the RDC sample.

The Change of Quantitative of HBeAg Can Predict the Efficacy of Peg-IFN-α 2a in HBeAgpositive CHB Patients

Objective To investigate the quantitation of hepatitis B e antigen (HBeAg) at week 24 in predicting the efifcacy of pegylated-interferon alfa-2a (Peg-IFN-α2a) in HBeAg-positive chronic hepatitis B (CHB) patients at week 48 and to find a useful predictor for treatment efficacy and investigate individualized treatment of antiviral therapy. Methods Ninety-six HBeAg-positive CHB patients with detectable HBeAg who were treated with Peg-IFN-α2a were enrolled in this trial. They were categorized into 3 groups according to the changes of HBeAg in week 24:HBeAg decline>2 log10 group (group A), HBeAg decline between 1 1og10-2 log10 (group B), HBeAg decline<1 log10 group (group C), and group C was randomly distributed into C1 and C2. The patients in group A, group B, and group C1 continued the original therapy and the patients in group C2 were given lamivudine plus Peg-IFN-α2a for 24 weeks. At week 48, the treatment efifcacy and hepatitis B virus covalently closed circular DNA (HBV cccDNA) in liver biopsies were analyzed. Results At week 48, mean reduction of serum HBV DNA:group A:5.8 log10 copies/ml, group B:3.8 log10 copies/ml, group C1:2.8 log10 copies/ml, group C2:5.7 log10 copies/ml, the reduction of HBV DNA in group A was greater than groups B and C1 (P<0.01), that in group C1 was greater than group C2 (P<0.01), the difference between groups B and C1 had no statistical signiifcance (P=0.19). Mean reduction of HBeAg:group A:2.7 log10S/CO, group B:1.9 log10S/CO, group C1:0.9 log10S/CO, group C2:1.5 log10S/CO, the difference among groups A, B and C1 and between groups C1 and C2 were statistically signiifcant (P<0.01). At week 48, HBV DNA undetectable rate in group A, group B, group C1 and group C2 were 87.5%, 34.5%, 17.4%and 81.9%, respectively, the rate in group A was greater than groups B and C1 (P<0.01),that in group C1 was greater than group C2 (P<0.01). HBeAg seroconversion rate were 75.0%, 24.1%, 13.0%and 22.7%, respectively, that in group A was greater than groups B and C1 (P<0.01). Group A had lower cccDNA in liver tissue than group B and group C1 (P<0.01). The difference of HBV cccDNA between groups B and C1 and that between groups C1 and C2 had no statistical signiifcance. Conclusions HBeAg decline > 2 log10 at week 24 in Peg-IFN-α 2a-treated hepatitis B patients suggested a better efficacy at week 48; HBeAg decline < 2 log10 at week 24 suggests a worse efficacy at week 48, the combined therapy of Peg-IFN-α and lamivudine could improve the clinical responses. The change of quantitative of HBeAg at week 24 may be used as a predictor of treatment effects at week 48.