Opto-acoustic modulator with a nematic liquid crystal

A liquid-crystal optical modulator working with acoustic signals is considered. It is shown that it can be operated also with white light up to frequencies of at least 1 MHz.     

Two-Phase Problems for Linear Elliptic Operators with Variable Coefficients: Lipschitz Free Boundaries are <Emphasis Type="Italic">C</Emphasis><Superscript><Emphasis Type="Italic">1,γ</Emphasis></Superscript>

We prove C ^1, regularity of Lipschitz free boundaries of two-phase problems for linear elliptic operators with Hölder continuous coefficients.     

On boundary behavior of harmonic functions in Hölder domains

We analyze the boundary behavior of harmonic functions in a domain whose boundary is locally given by a graph of a Hölder continuous function. In particular we give a non-probabilistic proof of a Harnack-type principle, due to Bañuelos et al. and study some properties of the harmonic measure.     

Photoluminescence spectroscopy of carbon nanotube bundles: evidence for exciton energy transfer

We investigate photoluminescence of nanotube bundles. Their spectra are explained by exciton energy transfer between adjacent tubes, whereby excitation of large gap tubes induces emission from smaller gap ones. The consequent relaxation rate is faster than nonradiative recombination, leading to enhanced photoluminescence of acceptor tubes.     

Embrittlement of nano-scale structures

A dealloyed surface layer formed on a Cu-30 Au alloy due to a corrosion process is capable of inducing intergranular cleavage of the normally ductile substrate during subsequent mechanical loading. The structure of the dealloyed layer consists of nanoscale pores that were formed by the selective removal of copper atoms during the anodic polarization. To contribute to the understanding of environmentally — induced embrittlement, we presently compute the stress state within the porous layer and in the bulk substrate due to the eigenstraining by the dealloying. The results of the calculations shows that a tensile stress state exists in the porous dealloyed layer while a compressive stress state is generated in the substrate. Implications on the “film-induced cleavage” model of stress corrosion cracking mechanism are discussed.