Study of fast switching processes due to electric and magnetic fields--an NMR approach.

Solid state NMR techniques have been developed to investigate dynamic molecular effects (e.g., molecular reorientations) due to simultaneously applied external electric fields on electrically sensitive materials such as liquid crystals (LC), liquid crystalline polymers (LCP) and polymeric electrets. Such effects can be observed only on relatively thin systems (10-200 microm). That means that many scans are necessary to achieve a sufficiently high signal-to-noise-ratio in the spectra (500-1000 scans). If the material is also magnetically sensitive, the electric field can be used to orient molecules in a starting orientational state and by switching-off the voltage to access fast reorientation processes in the magnetic field B0. Until now, the behaviour of orientable molecular systems under the influence of electric fields has been investigated by means of a more or less quasistatic approach (LCP: 100 V, electrets: 1 kV) in equilibrium states. The achievable time resolution depends on the desired signal-to-noise-ratio. For the case of proton NMR this means a time resolution of about 10 min. However, very often switching processes occur on a much shorter time scale. Using conventional techniques it is impossible to observe fast (ca. 100 micros) electrically or magnetically induced reorientation processes. In this work, we present a concept to overcome the problems outlined above and to extend the area of our current in situ NMR investigations on thin electrically-switched or poled polymeric layers. The basic idea is to include synchronized electric pulses during the NMR experiment using the preparation and/or mixing periods of a 1D or 2D pulse sequence for the application of an orienting field (electric or magnetic) and to use the reversibility of the molecular switching phenomenon to achieve a sufficient signal-to-noise-ratio. The techniques extend the range of possible investigations from about 100 micros to approximately T1 for correlated spectra (and to longer times of applied fields for uncorrelated spectra). Results are shown for a nematic LC and a nematic polymer having a similar side chain.

A portable absorption-fluorometer for detection of organic substances in fluids.

Using the method of multipath-saturation fluorescence, which considers both fluorescent as well as nonfluorescent substances, the total absorption coefficient can be determined with high sensitivity. This new fluorescence method is appropriate, e.g. for in-situ applications. Thus a portable absorption-fluorometer has been constructed. The main part of the device is a multireflection cell based on a design of Herriott with a 1 cm quartz-cuvette. Two pairs of spherical dielectric mirrors are used to realize the multireflection of the excitation radiation in the UV and blue spectral range. The combination of a cylindrical and a convace mirror leads to a long pathway of the excitation radiation and, thus, to a full absorption by the fluid. A first experiment has been performed with drinking water samples defined polluted by non-fluorescent p-nitrophenol and 2-nitroaniline. Based on the method of multipath-saturation fluorescence a good correlation to the substance concentration was achieved, whereas the conventional absorption failed.

[Studies and computer analyses on the kinetics of nephrotropic contrast media in patients with different kidney function]. / Untersuchungen und Computeranalysen zur Kinetik nephrotroper Röntgenkontrastmittel bei Patienten mit unterschiedlicher Nierenfunktion.

The local quantity of the contrast excretion depends on the filtration rate and the plasma level. Since the latter is influenced by dosage and kind of application from this result immediate practical consequences for the excretion urography, for which at present a large dose and the bolus injection are preferred.

[Urethral carcinoma in the female]. / Das Urethralkarzinom der Frau

It is reported on a case of the rare carcinoma of the female urethra. In the 68-year-old patient the tumour was removed by electrocaustic excision, a suprapubic incision into the bladder was made and local radiotherapy was performed.