Epitaxial Cubic Silicon Carbide Photocathodes for Visible-Light-Driven Water Splitting

Cubic silicon carbide (3C-SiC) material feature a suitable bandgap and high resistance to photocorrosion. Thus, it has been emerged as a promising semiconductor for hydrogen evolution. Here, the relationship between the photoelectrochemical properties and the microstructures of different SiC materials is demonstrated. For visible-light-derived water splitting to hydrogen production, nanocrystalline, microcrystalline and epitaxial (001) 3C-SiC films are applied as the photocathodes. The epitaxial 3C-SiC film presents the highest photoelectrochemical activity for hydrogen evolution, because of its perfect (001) orientation, high phase purity, low resistance, and negative conduction band energy level. This finding offers a strategy to design SiC-based photocathodes with superior photoelectrochemical performances.     

Experimental and numerical study of the switching dynamics of Raman fiber lasers

We present an experimental and numerical survey of the switching behavior of cascaded Raman fiber lasers (RFLs). When these lasers are switched on, the output power shows a pulsing behavior where the pulse powers strongly exceed the steady-state output powers. The influence of the pump-laser and fiber properties of a RFL on this dynamical behavior is investigated both experimentally and numerically, where experiments and simulations showed good qualitative agreement. PACS 42.55.Wd; 42.55.Ye; 42.60.Lh     

BEM with linear complexity for the classical boundary integral operators

Alternative representations of boundary integral operators corresponding to elliptic boundary value problems are developed as a starting point for numerical approximations as, e.g., Galerkin boundary elements including numerical quadrature and panel-clustering. These representations have the advantage that the integrands of the integral operators have a reduced singular behaviour allowing one to choose the order of the numerical approximations much lower than for the classical formulations. Low-order discretisations for the single layer integral equations as well as for the classical double layer potential and the hypersingular integral equation are considered. We will present fully discrete Galerkin boundary element methods where the storage amount and the CPU time grow only linearly with respect to the number of unknowns.

     

Modern Trends in Organic Light-Emitting Devices (OLEDs)

Synthesis of crosslinkable small and large organic molecules having OLED properties will be presented. Three strategies for the construction of multilayer devices will be described. In the first case small, well-defined OLED-molecules are functionalized with oxetanes as crosslinker. The second case deals with polymers having OLED active units in the main chain and pendant crosslinkers and finally it was shown that styrene polymers with pendant OLED functions and crosslinkers can be applied for the construction of such multilayer and multicolour devices.     

Diffusion-Advection in Cellular Flows with Large Peclet Numbers

(Accepted January 2, 2003) Published online April 10, 2003 Communicated by F. Otto     

Selective oxidative debenzylation of mono- and oligosaccharides in the presence of azides

When using benzyl ethers as permanent protecting groups in oligosaccharide synthesis selective oxidative debenzylation with NaBrO(3) + Na(2)S(2)O(4) under biphasic conditions is efficient and compatible with anomeric azides and many other functions.