Rheological behavior of highly filled ethylene propylene diene rubber compounds

The rheological behavior of highly filled ethylene propylene diene rubber (EPDM) compounds was studied with respect to the effect of curative system, grafted rubber, shear rate, temperature and die swell using a Monsanto Processability Tester (MPT) to gain an understanding of the molecular parameters that control the surface finish. All systems show pseudoplastic behavior. At a particular shear rate, shear viscosity increases with blend ratio. The dependence of flow behavior on extrusion velocity indicates a surface effect. The extrudate die swell and maximum recoverable deformation are related by a linear relationship, which is independent of sulfur/accelerator ratio, extrusion temperature and shear rates and blend ratio. The principal normal stress difference increases nonlinearly with shear stress. Activation energy decreases with shear rate in most cases. The faster relaxing system produces extrudate of better surface quality.     

Mechanical properties of malleable iron after isothermal quenching by various regimes

In recent years the range of application of cast irons in a heat treated state has widened. Isothermal quenching of irons that provides a favorable combination of strength and ductile parameters commonly inherent in steels is the most promising. The present work concerns the effect of regimes of isothermal quenching on the mechanical properties of cast iron. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 29–31, December, 1998.     

Loss of KAI1 messenger RNA expression in both high-grade and invasive human bladder cancers

The molecular mechanisms responsible for metastasis are not fully understood. Recently, expression of the KAI1 gene on human chromosome 11p11.2 was found to be down-regulated in metastatic prostate cancer cell lines compared with normal human prostate, suggesting that KAI1 may be a metastasis suppressor gene. The aim of this study was to investigate whether there is reduced expression of KAI1 in late-stage bladder cancer. Sixty-six paraffin-embedded bladder tissue sections were analyzed for KAI1 mRNA by in situ hybridization. Nineteen of these were from patients with no histological evidence of bladder cancer, and 47 were from papillary transitional cell carcinomas (TCCs); of these, 16 were highly invasive. KAI1 mRNA was highly expressed in the specimens of normal bladder (11 of 11; 100%), inflammatory bladder (5 of 8; 63%), and noninvasive papillary TCCs of grades 1 and 2 (15 of 24; 63%), compared to grade 3 papillary TCCs (1 of 7; 14%) or invasive TCCs (1 of 16; 6%). The differences in expression between local and invasive disease were statistically significant (P 相似文献   

Studies of the structure of the N-terminal domain from the Y4 receptor - a G protein-coupled receptor - and its interaction with hormones from the NPY family

Binding of peptide hormones to G protein-coupled receptors is believed to be mediated through formation of contacts of the ligands with residues of the extracellular loops of family 1 GPCRs. Here we have investigated whether additional binding sites exist within the N-terminal domain, as studied in the form of binding of peptides from the neuropeptide Y (NPY) family to the N terminus of the Y4 receptor (N-Y4). The N-terminal domain of the Y4 receptor has been expressed in isotopically enriched form and studied by solution NMR spectroscopy. The peptide is unstructured in solution, whereas a micelle-associated helical segment is formed in the presence of dodecylphosphocholine (DPC) or sodium dodecylsulfate (SDS). As measured by surface plasmon resonance (SPR) spectroscopy, N-Y4 binds with approximately 50 microM affinity to the pancreatic polypeptide (PP), a high-affinity ligand to the Y4 receptor, whereas binding to neuropeptide Y (NPY) and peptide YY (PYY) is much weaker. Residues critical for binding in PP and in N-Y4 have been identified by site-directed mutagenesis. The data indicate that electrostatic interactions dominate and that this interaction is mediated by acidic ligand and basic receptor residues. Residues of N-Y4 are likely to contribute to the binding of PP, and in addition might possibly also help to transfer the hormone from the membrane-bound state into the receptor binding pocket.