Determination of excitation profile and dielectric function spatial nonuniformity in porous silicon by using WKB approach

We develop an analytical model based on the WKB approach to evaluate the experimental results of the femtosecond pump-probe measurements of the transmittance and reflectance obtained on thin membranes of porous silicon. The model allows us to retrieve a pump-induced nonuniform complex dielectric function change along the membrane depth. We show that the model fitting to the experimental data requires a minimal number of fitting parameters while still complying with the restriction imposed by the Kramers-Kronig relation. The developed model has a broad range of applications for experimental data analysis and practical implementation in the design of devices involving a spatially nonuniform dielectric function, such as in biosensing, wave-guiding, solar energy harvesting, photonics and electro-optical devices.

Attenuation of depression of muscle protein synthesis induced by lipopolysaccharide, tumor necrosis factor, and angiotensin II by beta-hydroxy-beta-methylbutyrate

beta-Hydroxy-beta-methylbutyrate (HMB; 50 microM) has been shown to attenuate the depression in protein synthesis in murine myotubes in response to lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) with or without interferon-gamma (IFN-gamma), and angiotensin II (ANG II). The mechanism for the depression of protein synthesis by all three agents was the same and was attributed to activation of double-stranded RNA-dependent protein kinase (PKR) with the subsequent phosphorylation of eukaryotic initiation factor 2 (eIF2) on the alpha-subunit as well as increased phosphorylation of the elongation factor (eEF2). Myotubes expressing a catalytically inactive PKR variant, PKRDelta6, showed no depression of protein synthesis in response to either LPS or TNF-alpha, confirming the importance of PKR in this process. There was no effect of any of the agents on phosphorylation of mammalian target of rapamycin (mTOR) or initiation factor 4E-binding protein (4E-BP1), and thus no change in the amount of eIF4E bound to 4E-BP1 or the concentration of the active eIF4E.eIF4G complex. HMB attenuated phosphorylation of eEF2, possibly by increasing phosphorylation of mTOR, and also attenuated phosphorylation of eIF2alpha by preventing activation of PKR. These results suggest that HMB may be effective in attenuating muscle atrophy in a range of catabolic conditions.

In-situ measurement and the reconstruction in 3D of femtosecond inscription induced complex permittivity modification in glass

We demonstrate a new approach to in-situ measurement of femtosecond laser pulse induced changes in glass enabling the reconstruction in 3D of the induced complex permittivity modification. The technique can be used to provide single shot and time resolved quantitative measurements with a micron scale spatial resolution.