STM Studies of Synthetic Peptide Monolayers

We have used scanning probe microscopy to investigate self-assembled monolayers of chemically synthesized peptides. We find that the peptides form a dense uniform monolayer, above which is found a sparse additional layer. Using scanning tunneling microscopy, submolecular resolution can be obtained, revealing the alpha helices which constitute the peptide. The nature of the images is not significantly affected by the incorporation of redox cofactors (hemes) in the peptides.Comment: 4 pages, 3 figures (4 gifs); to appear in the Proceedings of the XIIth Int. Winterschool on Electronic Properties of Novel Materials "Molecular Nanostructures", Kirchberg/Tyrol, Febr. 199

High-temperature-grown buffer layer boosts electron mobility in epitaxial La-doped BaSnO3_3/SrZrO3_3 heterostructures

By inserting a SrZrO$_3$ buffer layer between the film and the substrate, we demonstrate a significant reduction of the threading dislocation density with an associated improvement of the electron mobility in La:BaSnO$_3$ films. A room temperature mobility of 140 cm$^2$ V$^{-1}\text{s}^{-1}$ is achieved for 25-nm-thick films without any post-growth treatment. The density of threading dislocations is only $4.9\times 10^{9}$ cm$^{-2}$ for buffered films prepared on (110) TbScO$_3$ substrates by pulsed laser deposition.Comment: 5 pages, 4 figure

Tailoring of the luminescent ions local environment in optical fibers, and applications

The chapter is situated in the fields of fiber materials sciences and technologies (particularly dealing with the fiber glass compositions and luminescent ion doping, and transparent glass ceramic optical fibers), and applications such as fiber lasers and amplifiers. We propose to present a review of research activities on rare-earth (RE) and transition metals (TM) doped silica-based optical fibers, aiming at understanding theier spectral properties, and particularly some of their optical transitions that will allow interesting and alternative applications. Silica, as opposed to alternative, low temperature materials, is chosen for practical and economical reasons. Selected RE and TM ions are studied both as probes of their local environment and for their application potentials. In this chapter, we will focus on erbium (Er) ions for the potential spectral 'tailoring' of its gain curve at 1.55 $\mu$m, thulium (Tm) as local environment probe along both near infrared transitions around 0.8 and 1.47 $\mu$m, and chromium (Cr) for the sensitivity of valency and spectroscopy to the glass composition and its potential as saturable absorber in lasers. We will present some extensive studies on the influence of the local environment on dopants: such as (but not limited to) energy transfer mechanisms between rare-earth ions of same nature (Tm-Tm) or different nature (Yb-Tm), effect of the local phonon energy on Tm ions emission efficiency, broadening of Er ions emission induced by oxide nanoparticles grown in situ during the fabrication process, etc. Knowledge of these effects is essential for photonics applications, and many studies are under progress or are still needed in this field. The potential of some applications which could benefit from the basic studies on materials are also numerically studied : 0.8-$\mu$m thulium-doped fiber laser, so-called S-band (1.47 $\mu$m) thulium-doped amplifier for telecommunications and laser applications, sensitisation of Tm-based devices using ytterbium sensitized ions.Comment: arXiv admin note: substantial text overlap with arXiv:0911.168

Fast image processing with constraints by solving linear PDEs

We present a general framework that allows image filtering by minimization of a functional using a linear and positive definite partial differential equation (PDE) while also permitting to control the weight of each pixel individually. Linearity and positive definiteness allow to use fast algorithms to calculate the solution. Pixel weighting allows to enforce the preservation of edge information without the need for nonlinear diffusion by making use of information coming from an external source. The proof of existence and uniqueness of the solution is outlined and based on that a numerical scheme for finding the solution is introduced. Using this framework we developed two applications. The first is simple and fast denoising, which incorporates an edge detection algorithm. In this case the functional is designed to enhance the weight of the approximation term over the smoothing term at those places where an edge is detected. The second application is a background suppression algorithm that is robust against noise, shadows thrown by the object, and on the background and varying illumination. The results are qualitatively not quite as good as the ones obtained with nonlinear PDEs, but this disadvantage is compensated by the processing speed, which allows analysis of a 320×240 color frame in about 0.3s on a standard PC