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the region of the respective kinks, 20-22 Á1 2 34567/mol and surface pressure ca. 15 dyn/cm, the viscosities increase 20-fold to ca. 20 (mdyn s) / cm. The viscosity displayed by stearic acid appears to arise principally from tail-group entanglement.15 The viscoelasticity observed with the fatty alcohols, with dipalmitoyl lecithin, and with stearic acid on water containing trivalent ions may be interpreted as showing the influence of the head group interaction mediated by the substrate.2,15•17 Valinomycin is disklike with very short pendant groups; neither stearic effects nor van der Waals attraction of the valyl groups appear to contribute to the viscosity. On the other hand, one would expect the polar group interaction might. Clearly, the factors contributing the viscoelastic behavior of monolayers are more subtle than expected.In conclusion, the work presented here establishes that monolayers of valinomycin have an anomalously low vis-

A novel and compact nanoindentation device for in situ nanoindentation tests inside the scanning electron microscope AIP Advances 2, 012104 (2012) Invited Review Article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions Rev. Sci. Instrum. 82, 121101 (2011) Nanometer optomechanical transistor based on nanometer cavity optomechanics with a single quantum dot J. Appl. Phys. 110, 114308 (2011) Breakover mechanism of GaAs photoconductive switch triggering spark gap for high power applications J. Appl. Phys. 110, 094507 (2011) Additional information on J. Appl. Phys. co-doped Y 2 BaZnO 5 near-infrared up-converting phosphors with organic photovoltaic devices is reported. We show that it is possible to obtain a J sc of 16 lA cm À2 under 986 nm illumination ($390 mW cm À2 corresponding to $37 suns) leading to an up-conversion external quantum efficiency (g UC EQE ) of 0.0052%. Through modification of the organic photovoltaic devices to incorporate transparent electrodes we show that g UC EQE could be increased to 0.031 %, matching that achieved in amorphous-Si:H PV cells. Accounting for the full spectral range that may be absorbed by the phosphor ($870-1030 nm) yields an up-conversion power conversion efficiency (g UC PCE ) of 0.073% which again could be improved to 0.45% using transparent electrodes. This technique for utilizing the near-infrared spectral region may therefore offer a potential route to improving the performance of organic photovoltaic devices as research into discovering high-efficiency up-converting phosphors continues to provide improved materials. V C 2012 American Institute of Physics.

Abstract:The assumptions underlying the extraction of micellar aggregation numbers by means of applying the mass action law to the concentration dependence of i3C Nuclear Magnetic Resonance (NMR) shift data are discussed. Such data are presented for sodium dodecylsulfate and it is shown that the extracted aggregation numbers are far too small. It is argued that this is in part due to a failure of the mass action law to describe the micellization process but also due to covariance in the parameters of the mass action law. We also suggest a way to analyse 13C shifts from surfactant systems that is void of artefacts due to changes in volume magnetic susceptibilities and other "unwanted" artefacts. Finally, we point out that by combining 13C shifts with the fraction of micellized surfactant (as measured by for instance self diffusion coefficients) it should be possible to monitor changes in micellar shapes as the conditions are changed.

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