Zur Erkennung sehr geringer Mengen gel?ster freier Phosphors?ure

Ohne Zusammenfassung     

Der Oktaeder-Oktant oder ein Heptaeder

Ohne Zusammenfassung     

Zur Titrirung der Essigs?ure

Ohne Zusammenfassung     

Design and fabrication of AlGaAs/GaAs phase couplers for optical integrated-circuit applications

As integrated electronic circuits based on GaAs are getting faster and more complex and the relatively new fiber optic communication industry is expanding into new markets, such as shipboard communication links, the need for high-speed optical signal processing in a GaAs-based system has become increasingly evident. The economy and flexibility of fabricating both electronic and optical circuits on the same wafer promises significant increases in the computing power and speed of large distributed systems (those involving more than a few medium-density chips). The obvious medium for integration of optics with electronics is GaAs. High-speed ICs utilizing GaAs MESFETS are already in the marketplace, as are GaAs/AlGaAs laser diodes and detectors. Thus the two building blocks exist and only wait to be stacked together in a useful manner. What must hold these together is any combination of passive waveguides, modulators, switches, or optical fibers which will provide high-speed links between several electronic systems. It does not matter that these systems may be miles apart or on the same wafer: the interconnecting optical circuits are the same except for the possible insertion of an optical fiber.     

Single dopant diffusion in semiconductor technology

The paper deals with the analysis of pair diffusion models in semiconductor technology. The underlying model contains reaction‐drift‐diffusion equations for the mobile point defects and dopant‐defect pairs as well as reaction equations for immobile dopants which are coupled with a non‐linear Poisson equation for the chemical potential of the electrons. For homogeneous structures we present an existence and uniqueness result for strong solutions. Starting with energy estimates we derive further a priori estimates such that fixed point arguments due to Leray–Schauder guarantee the solvability of the model equations. Copyright © 2004 John Wiley & Sons, Ltd.     

Chlorophyll fluorescence biosensor for the detection of herbicides

A biosensor is described for the detection of triazine and phenylurea herbicides in drinking water by kinetic measurements of endogenous chlorophyll fluorescence in isolated chloroplasts from higher plants. The pocket-size device uses a diode laser for simultaneous excitation of sample and reference channels, and photodiodes for detection of the emitted light. The biological material can be supplied as a freeze-dried powder, stable for 21 days at room temperature, for 6 weeks at 4 ( degrees )C or for at least 9 months at -20 ( degrees )C. The detection of 0.1 microg/l of a single herbicide, as required by European Community legislation on drinking water quality, can be achieved without prior extraction of the sample.