Emission spectral analysis using photographic plates treated with a phenidone developer

When spectral photographic plates are not treated in the conventional metol-hydroquinone developer, but in a phenidone developer, a strong increase in the sensitivity and a certain increase in the contrast are observed. With phenidone development, weak lines are intensified, permitting the lowering of the limits of detection and determination. The increase in the contrast increases the slope of the concentration-calibration curves and hence the concentrational sensitivity of the spectral analyses. This is illustrated in the curves for the determination of Si and Mn in low-alloy steels. Further sensitivity can be obtained by following the phenidone development by a chromium intensifying process.     

Untersuchungen über die Kinetik der Oxydation von 1,2,4-Trimethylbenzol in essigsaurem Medium

Zusammenfassung Bei der Oxydation von 1,2,4-Trimethylbenzol in essigsaurem Medium wurde der Einfluß des Mediums sowie des Verhältnisses Kohlenwasserstoff/Medium und der Einfluß verschiedener Kobalt- bzw. Bromverbindungen auf das Anfangsstadium des Prozesses eingehend untersucht.

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Kinetics of the oxidation of 1.2.4-trimethylbenzene in an acetic acid medium

In the oxidation of 1.2.4-trimethyl-benzene in an acetic acid medium, the influence of the medium, as well as that of the hydrocarbon/medium ratio and the effect of various cobalt and bromine compounds have been studied in detail.

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Mit 4 Abbildungen     

Optical pump-terahertz probe spectroscopy of dyes in solutions: probing the dynamics of liquid solvent or solid precipitate?

The optical pump-terahertz probe spectroscopy was used together with ab initio calculations and molecular dynamics simulations to investigate ultrafast dynamics following electronic excitation of Coumarin 153 and TBNC (2,11,20,29-tetra-tert-butyl-2,3-naphtalocyanine) dyes in polar solvents. By scanning the terahertz waveform for different pump-probe delays this experimental technique allows us to obtain two dimensional spectra directly reflecting the temporal response of the system. A distinct signal was obtained for TBNC in chloroform, 2-propanol, and n-butanol, while no signal was recorded for Coumarin 153 in either of these solvents. We explain the nonequilibrium signal detected in TBNC solutions by the presence of a solid, polycrystalline phase of the dye resulting from irradiating the solution by intense optical pulses.     

Adhesion of protein crystals: Measurement of the detachment force

The degree of adhesion of protein crystals, heterogeneously nucleated and grown on different supports (e.g. glass plates and plates coated with poly‐L‐lysine, hexamethyl‐disilazane and silicon) is measured directly with a purposely‐developed technique. The sticking force crystal/support is determined by means of a flexible glass fibre, which bending is calibrated by means of series of weights. In this way an elastic constant, specific for each glass fiber is determined individually. Appropriate glass fibres with relative bending less than 10% (Hook's law) are used. The force which is necessary to be exerted, by means of a micro‐manipulator, in order to detach the crystal from the support is taken as a quantitative measure for the adhesion strength. Forces between 10 N cm^‐2 and 1 N cm^‐2 for differently oriented tetragonal hen‐egg‐white lysozyme and cubic ferritin crystals, and 0.1 N cm^‐2 for rhombohedral (porcine) insulin and orthorhombic trypsin crystals are measured. The tetragonal HEWL and rhombohedral insulin crystals show anisotropy of the adhesion strength. In contrast, the cubic ferritin crystals are isotropic also in this respect. For comparison purposes adhesion measurements are performed with NaCl and sugar crystals. An attempt is made to evaluate also the adhesion energy of the protein crystals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Non-linear modeling of bioconcentration using partition coefficients for narcotic chemicals

Bioconcentration factors (BCFs) have traditionally been used to describe the tendency of chemicals to concentrate in aquatic organisms. A reexamination of the log-log QSAR between the BCF and K OW for non-congener narcotic chemicals is presented on the basis of recommended data for fish. The model is extended to give a simple correlation between BCF and the toxicity of highly, moderately and weakly hydrophilic chemicals. For the first time, in this study an equation for calculating BCF was applied in a QSAR model for predicting the acute toxicity of chemicals to aquatic organisms.     

Simulation of chemical metabolism for fate and hazard assessment. V. Mammalian hazard assessment

Animals and humans are exposed to a wide array of xenobiotics and have developed complex enzymatic mechanisms to detoxify these chemicals. Detoxification pathways involve a number of biotransformations, such as oxidation, reduction, hydrolysis and conjugation reactions. The intermediate substances created during the detoxification process can be extremely toxic compared with the original toxins, hence metabolism should be accounted for when hazard effects of chemicals are assessed. Alternatively, metabolic transformations could detoxify chemicals that are toxic as parents. The aim of the present paper is to describe specificity of eukaryotic metabolism and its simulation and incorporation in models for predicting skin sensitization, mutagenicity, chromosomal aberration, micronuclei formation and estrogen receptor binding affinity implemented in the TIMES software platform. The current progress in model refinement, data used to parameterize models, logic of simulating metabolism, applicability domain and interpretation of predictions are discussed. Examples illustrating the model predictions are also provided.     

Photocatalytic oxidation of pharmaceuticals on thin nanostructured Zinc Oxide films

The photocatalytic activity of thin ZnO films in the photocatalytic oxidation of the pharmaceuticals, paracetamol and chloramphenicol (Levomycetin) is reported. The films annealed at 500°C exhibit the highest activity. They have a wurtzite-like structure and consist of conducting branches, which are the spinodal decomposition products.