Microstructure Evolution of a 10Cr Heat-Resistant Steel during High Temperature Creep

The microstructure evolution of a 10Cr ferritic/martensitic heat-resistant steel during creep at 600℃ was investigated in this work.Creep tests demonstrated that the 10Cr steel had higher creep strength than conventional ASME-P92 steel at 600℃.The microstructure after creep was studied by transmission electron microscopy,scanning electron microscopy and electron probe microanalysis.It was revealed that the martensitic laths were coarsened with time and eventually developed into subgrains after 8354 h.Laves phase was observed to grow and cluster along the prior austenite grain boundaries during creep and caused the fluctuation of solution and precipitation strengthening effects,which was responsible for the two slope changes on the creep rupture strength vs rupture time curve.It was also revealed that the microstructure evolution could be accelerated by stress,which resulted in the lower hardness in the deformed part of the creep specimen,compared with the aging part.     

Carboxy-terminal CFFL-sequence-specific monomeric protein geranylgeranyltransferase I from the eyes of the shrimp Penaeus japonicus

Protein geranylgeranyltransferase I from the eyes of Penaeus japonicus geranylgeranylates predominantly the sequence CFFL and Drosophila-specific Ras1 carboxyl termini, with the sequence CKML, as well as mammalian-specific G gamma carboxyl termini, with the sequence CAIL, but not the protein farnesyltransferase-specific sequence CVLS. The purified protein geranylgeranyltransferase I from shrimp was evidenced by immunoblotting and polyacrylamide gel electrophoresis under denaturing conditions to consist of single subunit of Mr 66,000 +/- 500. Since the active protein geranylgeranyltransferase I was found to have a relative mass of 67,000 +/- 1,000, the purified enzyme was deduced to be a monomer. The enzyme had an optimal pH of 8.0 with 100 mM Tris as the buffer and a K(m) of 7 +/- 2 microM with the synthetic peptide KCFFL as the substrate. The enzyme was inhibited by Zn++ and Mg++ ions at micromolar concentrations.     

Sustained TCR signaling is required for mitogen-activated protein kinase activation and degranulation by cytotoxic T lymphocytes

Requirements for T cell activation are not fully established. One model is that receptor occupancy and down-regulation are essential for activation, and another, not necessarily mutually exclusive, model is that sustained signals are important. Here we examine the importance of signal duration in T cell activation. First, we demonstrate that immobilized, but not soluble cross-linked, Abs to CD3 stimulate degranulation by CTL. The cross-linked Abs are not deficient in their ability to signal since they stimulate the same tyrosine phosphorylation pattern as immobilized Ab, but it is very transient relative to that stimulated by immobilized Ab. Furthermore, novel decreased migratory forms of Lck occur to a significant extent only after stimulation with immobilized Abs. A dramatic difference in the duration of signals is very evident when mitogen-activated protein kinase (MAPK) activity is examined. Immobilized anti-CD3 stimulates very high levels of MAPK activation that is still detectable 1 h after stimulation. In contrast, cross-linked Ab stimulates only transient and incomplete activation of MAPK. Taken together, these results suggest that TCR engagement and induction of tyrosine phosphorylation alone are not sufficient for T cell activation and that the duration of TCR-stimulated signals is critical to attain a functional response.