We consider Lorentz manifolds which carry a conformal gradient field with at least one zero. All such manifolds are necessarily locally conformally flat. If in addition the manifold is developable and the image of a development map is great enough one can describe the global conformal type by a 3-regular graph provided with two additional datas. We get this conformal invariants using certain conformal development maps into the projective standard quadric. All conformal diffeomorphisms of this projective quadric are nothing else than the projectivities of the ambient real projective space which preserve the quadric. In the proofs we often use this fact. As a by-product of a general existence theorem we give an infinite number of locally conformally flat Lorentz metrics on the differentiable manifold R^n which are in pairs not conformally equivalent.

The subject of this thesis is the development and the characterization of threedimensional electrode arrays for the electrostimulation of neural cells. For the development of the electrode fabrication process special attention was paid to the compatibility with existing CMOS processes. This allows the fabrication of electrodes and electronic control circuitry on the same substrate in a close distance without the need of further assembly techniques. The fabrication process of the electrode arrays essentially consists of electrodeposition of gold to form the threedimensional electrode structures and a further electrodeposition of iridium in order to improve the electrode characteristics significantly. Cylic voltammetry and impedance measurements were performed to characterize and compare the fabricated iridium electrode arrays with other common electrode materials such as platinum, gold and titanium nitride. It was shown that the iridium electrodes have lower impedances over the considered frequency ranges and higher permissible clamp voltages for electrostimulation. Furthermore a method and a device for scanning potential microscopy was developed. Measurements of the local potential distribution of different electrode configurations and electrode shapes in saline solutions have been performed using this scanning potential microscope. In this way results obtained by finite element simulations have been verified experimentally. It was also shown that the presented method offers a better spatial resolution than previously reported methods.

Microorganisms in biofilms are kept together by extracellular polymeric substances (EPS). The EPS are key molecules for the structure, function and organization of biofilms. Chemical and / or physical isolation methods are being used for the quantitative separation of EPS from biofilms. The yield of EPS depends on the method of isolation. Four different methods of EPS isolation were used in this work (separation by stirring and centrifugation, use of a cation exchange resin, extraction with formaldehyde and extraction with formaldehyde and NaOH) on pure culture biofilms of Pseudomonas aeruginosa and biofilms from sewage treatment systems. The isolation by stirring and centrifugation was suitable for pure culture biofilms. If calcium was present in the growth medium stirring and centrifugation alone was not sufficient. The isolation of EPS was successful with the cation exchange method. The method of choice for the isolation of EPS from environmental biofilms was the cation exchange method. EPS from pure culture biofilms of P. aeruginosa and P. fluorescens did not only consist of polysaccharides, but also of significant amounts of proteins. In environmental biofilms humic substances and DNA were found in addition to polysaccharides and proteins. Detailed studies of the EPS from P. aeruginosa showed, that the EPS consisted of 70 % (w/w) of alginate. Alginate showed a clear heterogeneity in relation to charge (acetylated and non-acetylated fraction) and molar mass. Neutral carbohydrates were not found in the EPS after total hydrolysis followed by thin layer chromatography. Proteins amounted to 28 % (w/w) of the EPS. It is assumable that this not only related to enzymes, but also structural proteins (e. g. lectins). Rhamnose lipids (mainly di-rhamno lipid) were also found in the EPS (small amount of 1 % (w/w)); these molecules may also play an important role in the development of the biofilm structure. By increasing the time of biofilm cultivation P. aeruginosa produced (related to cell number) more EPS (mainly alginate). The composition of the EPS was depending on the nutrient medium. In synthetic media high amounts of polysaccharides and almost no proteins (in contrast to rich media) were detected in the EPS. EPS of pure culture biofilms of P. fluorescens contained carbohydrates (57 % (w/w)) and proteins (28 % (w/w)). Acetyl groups (5 % (w/w)) and glucose and galactose after hydrolysis and thin layer chromatography were detected in the EPS. Possibly the exopolysaccharide of P. fluorescens is an acetylated galactoglucan. In the analyzed sludges of waste water treatment proteins followed by carbohydrates made up the main components of the EPS. Humic substances and small amounts of DNA were detected in these EPS. The EPS of aquatic biofilms contained large amounts of humic substances. Uronic acids were not detected in any analyzed environmental biofilm. Therefore acidic polysaccharides in these biofilms cannot play any role in the stabilization of biofilms by cross linking the EPS with multivalent cations. Instead of that, humic substances, nucleic acids and acidic proteins could be responsible for cross linking.

This work is subdivided in three chapters. In the first chapter the synthesis of a 7,7'-bridged 1,1'-Biisoquinoline by a Pomeranz-Fritsch-Reaction is described. This molecule was seperated in its atropisomers which racemice in solution. The influence of the solvent character to the rate of racemization was investigated. It has been shown that the more polar and the more protic the solvent is the higher is the rate of racemization. The second chapter introduces an easy synthetic route to 6-substituted Benzimidazo[2,1-a]isoquinolines and in the single case of a Furyl-substituent to Isoindolo[2,1-a]quinoxalins. The starting materials, ortho-Alkynyl-substituted Benzaldehydes, are prepared by Sonogashira-Coupling of the Bromobenzaldehydes with different substituted terminal Alkynes. The reaction of o,o'- Bis(phenylethinyl)-substituted Benzil with Hydroxylamine Hydrochloride leads to a rearranged Benzofluorenon. The formation is explained by a domino process including a cyclization-step, a Hetero-Diels-Alder reaction and the final rearrangement. In the third chapter the stereochemical outcome of the McMurry reaction is investigated depending on the length of a tether between the meta and meta'-position of an Bisbenzaldehyde. Only the short dioxapentandiyl tethered Bisbenzaldehyde forms streoselectiv the cis-product. Starting with the dioxaoctandiyl- or dioxatetradecandiyl-tethered Bisbenzaldehydes the thermodynamical more stable trans products are obtained. In a second part the regioselectivity of the oxidative photocyclization of these McMurry-products, leading to tethered Phenathrenes, has been investigated. The dioxapentandiyl- and the dioxaoctandiyl-substituted Stilbenes leads regioselectiv to the 4,5-disubstituted Phenathrenes. Whereas the longer dioxatetradecandiyl-tether allows a change in the product ratio and the 2,5-disubstituted Phenanthrene is obtained as the major product. In all cases no 2,7-Phenanthrene could be detected.

In the theoretical part of this dissertation theintroduction of the thermodynamics of mixtures is followed by the basicknowledge of lightscattering. The correlation between thermodynamics atthe one hand and lightscattering at the other is demonstrated. In the apparativeand practicel part the development, build and handeling of the high pressurecell and the carrying out of the light scattering experiments are shown.In the part "results and discussion" the interesting and partly surprisingresults are presentet and discussed.

Today the development of industrial CMOS processes with respect to minimum structure size allows the realisation of CMOS image sensors with a spatial resolution comparable to CCD image sensors. While CCD's still provide images of higher quality, CMOS sensors can take advantage of the possibility of monolithic integration of optical sensor devices with analog and digital signal processing as well as high flexibility with respect to sensor readout. CMOS technology allows the realisation of low-cost single-chip camera electronics with very low power consumption and application specific properties. As a basis for future developments of CMOS imaging systems frequently used concepts for optical sensor devices and sensor readout circuits are analysed with respect to noise, dynamic range, linearity and speed. It is shown, how to optimise sensor circuits with respect to these properties. To demonstrate the advantages of CMOS technology compared with CCD technology, two integrated image sensors are presented. The image rs provide a very high input dynamic range and perform on-chip image processing inspired by the funcionality of the human retina.

In this work the generation of shock-waves and short electrical pulses on nonlinear transmission lines (NLTL) showing transients down to 3.6 ps and amplitudes of 1V - are presented. Special emphasis is layed upon the development of monolithic integration of planar schottky-diodes and coplanar waveguide structures based on InP-semiconductor material. The methods of simulating nonliear propagation effects on NLTL, designing and technology of NLTL and at last the experimental investigations in order to measure the generatred transients both in the time domain and frequency domain are shown in detail.

The reactivity of the polycyclic ß,Y-unsaturated ketones under different conditions were investigated. The titled ketons were reacted with Lithiumaluminiumhidrid and Grignard reagents with following dehydratation of the resulted secondary and tertiary alkohol. The Bucherer reaction, thermolysis and photolysis of these ketones were carried out.

Ni/Mg/Al containing anionic clays of hydrotalcite-type structure with varying Ni/Mg ratio and constant Al content were synthesised by coprecipitation. Their composition and structure was determined by elemental analysis, XRD, TG-MS and DSC. Their calcination at 700-1000°C resulted in the transformation into the corresponding mixed metal oxides, with their structure depending on the calcination temperature. Temperature programmed reduction/oxidation and high temperature XRD studies were applied to study their reducibility, Ni dispersion and the oxidation of the formed metallic nickel particles. The partial oxidation of propane to syngas could be successfully performed at temperatures between 600 and 900°C over reduced Ni containing catalysts. The conversion of propane and the yield of syngas increased with increasing reaction temperature. The catalysts with a low to medium Ni content exhibited better catalytic performance than those with a higher Ni content or a conventional steam reforming catalyst used as reference. Coking was found to decrease with increasing reaction temperature and to increase with increasing Ni content. Since several factors characterising the catalysts (BET surface area, Mg content and available Ni surface) follow the same or the opposite trend with the Ni content, it was impossible to differentiate between these properties and their effect on the catalyst performance or coking. By the use of the best catalyst an at least two-fold increase in the yield of carbon monoxide and eight-fold increase in the yield of hydrogen was observed compared with the non-catalytic reaction. Further investigations were performed to study the influence of the feed ratio and the space velocity.

The non-destructive and contactless current detection is highly required for the function- and failure analysis of integrated circuits (ICs). Up to now, different measurement techniques have been proposed and introduced. No commercial measurement technique has been available for the application. The aim of this work was to develop a scanning current measurement technique, that allows to detect currents on ICs contactless. Micro-miniaturized magneto-resistive (MR) sensors were used for the current detection. The measurement principle is detecting and assessing the magnetic fields over the current carrying conducting line. Based on the MR sensors, a new probe was constructed. This probe enables parallel to the current detection, a topography measurement. Furthermore, different measurement techniques were introduced and successfully applied, for the AC-current detection in µA-range and in MHz-range on the test structures. Finally, the functionality of the scanning current measurement technique was demonstrated by the current detection on a real IC.