15,142 research outputs found
An inter-comparison of Arctic synoptic scale storms between four global reanalysis datasets
The Arctic is becoming more accessible as sea ice extent continues to decline, resulting in higher human exposure to Arctic storms. This study compares Arctic storm characteristics between the ECMWF-Interim Reanalysis, 55-year Japanese Reanalysis, NASA-Modern Era Retrospective Analysis for Research and Applications Version 2 and National Centre for Environmental Prediction-Climate Forecast System Reanalysis datasets between 1980 and 2017, in winter (DJF) and summer (JJA). It is shown that Arctic storm characteristics are sensitive to the variable used for storm tracking. Arctic storm frequency is found to be similar in summer and winter when using sea level pressure minima to track Arctic storms, whereas, the storm frequency is found to be higher in winter than summer when using 850 hPa relative vorticity to track storms, based on using the same storm tracking algorithm. It is also found that there are no significant trends in Arctic storm characteristics between 1980 and 2017. Given the sparsity of observations in the Arctic, it might be expected that there are large differences in Arctic storm characteristics between the reanalysis datasets. Though, some similar Arctic storm characteristics are found between the reanalysis datasets, it is found that the differences in Arctic storm characteristics between the reanalysis datasets are generally higher in winter than in summer. Overall, the results show that there are differences in Arctic storm characteristics between reanalysis datasets, but even larger differences can arise between using 850 hPa relative vorticity or mean sea level pressure as the storm tracking variable, which adds to the uncertainty associated with current Arctic storm characteristics
Many-body theory interpretation of deep inelastic scattering
We analyze data on deep inelastic scattering of electrons from the proton
using ideas from standard many-body theory involving {\em bound} constituents
subject to {\em interactions}. This leads us to expect, at large three-momentum
transfer , scaling in terms of the variable . The response at constant scales well in this variable.
Interaction effects are manifestly displayed in this approach. They are
illustrated in two examples.Comment: 10 pages, 4 figure
Intrinsic Spin Hall Effect in the presence of Extrinsic Spin-Orbit Scattering
Intrinsic and extrinsic spin Hall effects are considered together on an equal
theoretical footing for the Rashba spin-orbit coupling in two-dimensional (2D)
electron and hole systems, using the diagrammatic method for calculating the
spin Hall conductivity. Our analytic theory for the 2D holes shows the expected
lowest-order additive result for the spin Hall conductivity. But, the 2D
electrons manifest a very surprising result, exhibiting a non-analyticity in
the Rashba coupling strength where the strictly extrinsic spin Hall
conductivity (for ) cannot be recovered from the
limit of the combined theory. The theoretical results are discussed in the
context of existing experimental results.Comment: 5 pages, 2 figure
Film thickness measurements on five fluid formulations by the mercury squeeze film capacitance technique
The thinning characteristics of five fluids were studied by measuring film thickness as a function of time. The mercury squeeze film capacitance technique was used. All tests were performed at room temperature. The synthetic hydrocarbon plus a nematic liquid crystal, N-(p-methoxybenzylidene)-p-butylaniline, thinned according to a Newtonian model and retained its bulk viscosity. The synthetic hydrocarbon plus a phosphonate antiwear additive and the synthetic hydrocarbon plus n-hexadecanol produced residual thick films. The synthetic hydrocarbon base fluids and the synthetic hydrocarbon plus a paraffinic resin displayed viscosity increases during thinning, but no residual films were formed
Selective inhibition of phosphodiesterases 4, 5 and 9 induces HSP20 phosphorylation and attenuates amyloid beta 1-42 mediated cytotoxicity
Phosphodiesterase (PDE) inhibitors are currently under evaluation as agents that may facilitate the improvement of cognitive impairment associated with Alzheimer's disease. Our aim was to determine whether inhibitors of PDEs 4,5 and 9 could alleviate the cytotoxic effects of amyloid beta 1–42 (Aβ1-42) via a mechanism involving the small heatshock protein HSP20. We show that inhibition of PDEs 4,5 and 9 but not 3 induces the phosphorylation of HSP20 which, in turn, increases the co-localisation between the chaperone and Aβ1-42 to significantly decrease the toxic effect of the peptide. We conclude that inhibition of PDE9 is most effective to combat Aβ1-42 cytotoxicity in our cell model
The quenching of compressible edge states around antidots
We provide a systematic quantitative description of the edge state structure
around a quantum antidot in the integer quantum Hall regime. The calculations
for spinless electrons within the Hartree approximation reveal that the widely
used Chklovskii et al. electrostatic description greatly overestimates the
widths of the compressible strips; the difference between these approaches
diminishes as the size of the antidot increases. By including spin effects
within density functional theory in the local spin-density approximation, we
demonstrate that the exchange interaction can suppress the formation of
compressible strips and lead to a spatial separation between the spin-up and
spin-down states. As the magnetic field increases, the outermost compressible
strip, related to spin-down states starts to form. However, in striking
contrast to quantum wires, the innermost compressible strip (due to spin-up
states) never develops for antidots.Comment: submitted to Phys. Rev. Let
- …