Mechanical and tribological characterization nitrided Al-7075/Al2O3 metal matrix composites

This research is mainly intended to evaluate the effect of nitriding on the wear behaviour of Al2O3 reinforced aluminium-7075 metal matrix composite materials. The composites were prepared by using powder metallurgy process. The amount of Al2O3 in these composites was varied from 3% to 7% (by weight) in steps of 2%. Homogeneously mixed powder by using double cone mixture was compacted using hydraulic press with 60KN of load. The compaction load was optimized to get a equal density as base specimens,then the compacted specimens were sintered at 5400 C which is 80% of melting temperature aluminium base alloy. The sintered materials were nitrided with a temperature of 520°C for 72hrs. Two different set of specimens, namely, nitrided composites and non-nitrided composites specimens were tested for their wear resistance and hardness properties. Pin-on-disc equipment was used for wear testing and microhardness testing machine was used for hardness testing. Elemental X-Ray Diffraction technique (XRD) was used to ensure the diffusion of nitrogen to the surface of composites. After all the standard tests it was observed that the nitrided composites have shown better wear resistance than the non-nitrided composite

One-step immunopurification and lectinochemical characterization of the Duffy atypical chemokine receptor from human erythrocytes

Duffy antigen/receptor for chemokines (DARC) is a glycosylated seven-transmembrane protein acting as a blood group antigen, a chemokine binding protein and a receptor for Plasmodium vivax malaria parasite. It is present on erythrocytes and endothelial cells of postcapillary venules. The N-terminal extracellular domain of the Duffy glycoprotein carries Fya/Fyb blood group antigens and Fy6 linear epitope recognized by monoclonal antibodies. Previously, we have shown that recombinant Duffy protein expressed in K562 cells has three N-linked oligosaccharide chains, which are mainly of complex-type. Here we report a one-step purification method of Duffy protein from human erythrocytes. DARC was extracted from erythrocyte membranes in the presence of 1% n-dodecyl-β-D-maltoside (DDM) and 0.05% cholesteryl hemisuccinate (CHS) and purified by affinity chromatography using immobilized anti-Fy6 2C3 mouse monoclonal antibody. Duffy glycoprotein was eluted from the column with synthetic DFEDVWN peptide containing epitope for 2C3 monoclonal antibody. In this single-step immunoaffinity purification method we obtained highly purified DARC, which migrates in SDS-polyacrylamide gel as a major diffuse band corresponding to a molecular mass of 40–47 kDa. In ELISA purified Duffy glycoprotein binds anti-Duffy antibodies recognizing epitopes located on distinct regions of the molecule. Results of circular dichroism measurement indicate that purified DARC has a high content of α-helical secondary structure typical for chemokine receptors. Analysis of DARC glycans performed by means of lectin blotting and glycosidase digestion suggests that native Duffy N-glycans are mostly triantennary complex-type, terminated with α2-3- and α2-6-linked sialic acid residues with bisecting GlcNAc and α1-6-linked fucose at the core