Based on a two dimensional odd-parity superconducting order parameter for Sr 2 RuO 4 with p-wave symmetry, we investigate the single vortex and vortex lattice structure of the mixed phase near H c1 . Ginzburg-Landau calculations for a single vortex show a fourfold structure with an orientation depending on the microscopic Fermi surface properties. The corresponding extended London theory is developed to determine the vortex lattice structure and we find near H c1 a centered rectangular vortex lattice. As the field is increased from H c1 this lattice continuously deforms until a square vortex lattice is achieved. In the centered rectangular phase the field distribution, as measurable through µSR experiments, exhibits a characteristic two peak structure (similar to that predicted in high temperature and borocarbide superconductors).Typeset using REVT E X 10

We report on the self-healing behavior of a polyelectrolyte-based aqueous lubricant additive, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), during aqueous lubrication of an oxide-based tribosystem. Combined pin-on-disk tribometry and fluorescence microscopy experiments have shown that stable lubricating performance was enabled by means of rapid healing of the worn tribopair surface by polymers dissolved in the adjoining bulk lubricant. This rapid 'self-healing' of PLL-g-PEG is attributed to electrostatic interactions between the polycationic poly(L-lysine) (PLL) backbone of the polymer and negatively charged oxide surface. In contrast, a similar healing effect was not readily achievable in the case of methoxy-poly(ethylene glycol)-trimethylsilylether (Sil-PEG), a lubricant additive that is covalently bonded to the surface prior to tribological stress.

No abstract

Poly(methacrylic acid) (PMAA) brushes were grafted from Si/SiO2 substrates by means of immobilized-photoiniferter-mediated controlled radical polymerization. The employed UV setup was based on ultraviolet light-emitting diodes (UV-LEDs), which allowed for a precise control of the brush height with irradiation time, as observed by in situ quartz crystal microbalance experiments with dissipation monitoring (QCM-D). In contrast to many alternative approaches, it was shown that the novel UV source in combination with a photoiniferter renders lengthy postcleaning steps of the synthesized brushes unnecessary. Following characterization of the polymer layers by means of variable-angle spectroscopic ellipsometry (VASE) and static contact angle measurements, the lubrication properties of the PMAA brushes were investigated in macroscopic tribological experiments under low-contact-pressure, aqueous conditions. Results indicated that PMAA brushes have the potential to dramatically reduce sliding friction in an aqueous environment.

We have investigated the influence of a high-concentration salt solution (1 M NaCl) on the aqueous lubrication properties of ethylene glycol-based molecules, namely, alpha-methoxy-omega-mercaptopoly(ethylene glycol) (MW 5000 Da) and alpha-methoxy-omega-mercaptoheptakis(ethylene glycol) (MW 356 Da), which have been end-grafted onto polycrystalline gold surfaces at high surface density. Macroscopic-scale, yet nondestructive, pin-on-disk tribometry experiments revealed that a high concentration of sodium chloride is deleterious to the aqueous lubricating properties of both films under low-sliding-speed conditions. This behavior was observed to be closely associated with the more collapsed conformation of surface-grafted poly(ethylene glycol) polymer chains in concentrated salt solutions, as confirmed by quartz-crystal microbalance measurements.