Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications.

Silver tantalate (AgTaO3) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application.

Nanoscale structure and structural relaxation in Zr50Cu45Al5 bulk metallic glass.

Hybrid reverse Monte Carlo simulations of the structure of Zr50Cu45Al5 bulk metallic glass incorporating medium-range structure from fluctuation electron microscopy data and short-range structure from an embedded atom potential produce structures with significant fractions of icosahedral- and crystal-like atomic clusters. Similar clusters group together into nanometer-scale regions, and relaxation transforms crystal-like clusters into icosahedral clusters. A model refined against only the potential does not agree with the fluctuation microscopy data and contains few crystal-like clusters.

Increased Young's modulus and hardness of Col1a2oim dentin.

Mice harboring the Col1a2(oim) mutation (oim) express dentinogenesis imperfecta. To determine the effect of Col1a2 genotype on tissue mechanical properties, we compared Young's modulus and hardness of dentin in the 3 Col1a2 genotypes. Upper incisors were tested by nanoindentation. Genotype had a significant effect on Young's modulus, but there was not a simple mutant allele dosage relationship. The effect of genotype on hardness did not reach significance. Hardness and Young's modulus were greater near the dento-enamel junction than near the pulp chamber. Greater hardness and Young's modulus values near the dento-enamel junction reflected continued mineralization of the dentin following its initial synthesis. Analysis showed the mechanical data to be consistent with Fourier transform infrared and backscattered electron microscopy studies that revealed increased mineralization in oim bone. Analysis of the data suggests that clinical fragility of teeth in oim mice is not due to deficiencies of hardness or Young's modulus, but may be due to defects in post-yield behavior or resistance to fatigue damage.

Health surveillance for health care workers. A vital role for the occupational and environmental health nurse.

Health surveillance for the general health care worker includes surveillance for immunity to infectious diseases such as measles, mumps, rubella, varicella, and hepatitis B. Post exposure surveillance for bloodborne pathogens includes HIV, hepatitis B, and hepatitis C. Periodic surveillance of specialty practice areas as mandated by OSHA include workers exposed to lasers, radiation, formaldehyde, ethylene oxide, hazardous drugs, anesthetic gases, and tuberculosis.

Stimulation of human polymorphonuclear leukocyte superoxide anion radical production by tumor promoters.

Comparison was made of the ability of the potent tumor promoter phorbol myristate acetate (PMA), as well as less active PMA analogs and non-phorbol ester tumor promoters, to stimulate superoxide anion radical (O-.2) production by human polymorphonuclear leukocytes (PMN). The rate of O-.2 production was found to correlate with the tumor-promoting activity of the phorbol esters as opposed to their inflammatory activity. Mezerein and telocidin B were slightly better stimulators of O-.2 production than PMA. Acetic acid was inactive. These data are discussed in terms of a possible role for O-.2 and other reactive oxygen species in tumor promotion.