Personal neutron dosimetry in the space station MIR and the Space Shuttle

A passive neutron dosemeter based on nuclear track detectors and TLD's was used in 1995 and 1997 on the MIR station and in Space Shuttle flights to MIR. As it is equipped with neutron converters and shieldings of different types the track detector system allows the neutron dose equivalent to be determined in rough energy intervals. The results of the measurements on the MIR station and in the Space Shuttle flights are presented and the influence of charged particles in the complex mixed radiation field in space is discussed. Improvements are possible by means of a new active neutron dosemeter which is under development at the PTB. First measurements with a prototype in the high-energy reference fields at CERN are presented and discussed.     

Surface enhanced Raman scattering (SERS): Annealing the silver substrate

Silver films, deposited at 120 K in UHV, were slowly warmed to room temperature, Characteristic intensity variations of the inelastic background (I), of disorder induced Raman scattering from phonons (II) and of the SERS signal from adsorbed pyridine have been observed. In the case of (I) and (II) these are explained by the bulk concentration of point defects, in the SERS case by annealing of atomic scale surface roughness.     

Der thermische Faktor in der Graschromatographie

Ohne Zusammenfassung     

A sensitive fluorimetric assay for cationic surfactants

Summary A new fluorimetric assay for cationic surfactants is based on their capability of quenching the fluorescence of 8-octadecyloxypyrene-1,3,6-trisulfonate (PTS-18). It is specific for cationic surfactants which can be determined in the 40–400 g concentration range. The method is considered to be advantageous over former methods in that it only requires addition of the sample solution to the fluorophore solution, followed by measurement of fluorescence intensity of the probe. This is in contrast to existing methods where the detergent/dye ion pair has to be extracted before measurement.     

Chromatography of xanthines on ion-exchange resins.

Short columns of a 4% crosslinked cation-exchange resin gave good chromatography of xanthines, including caffeine, theophylline and hypoxanthine, and related polar aromatic compounds. Elution volumes and sequences can be modified by changing pH, solvent composition and resin counter-ion. A macroporous cation-exchange resin showed exaggerated counter-ion effects. A method is described for determining caffeine and theophylline in blood serum, using the 4% crosslinked resin with aqueous sodium phosphate eluent of pH 7.5; the temperature was 65 degrees. Detection limits are 10 ng and less.     

Beiträge zur Gruppentheorie IX

Ohne ZusammenfassungR.Baer zum 60. Geburtstag     

Optimization of a kinetic-catalytic method by use of a numerical model and the simplex method

Optimization of a kinetic-catalytic method based on a numerical model is demonstrated for the copper(II)-catalyzed decomposition of hydrogen peroxide in the presence of pyridine. The responses are calculated as initial rates of the catalytic reaction after calculating the equilibrium distributions of all species in the reaction mixture. Simulation of response surfaces as well as simplexes showed optimal concentrations for hydrogen peroxide, pyridine and pH. Experimental verifications of the simulated reaction conditions showed that the catalytic determination of copper down to 1.5 x 10^-7 M is possible.