Untersuchung von Schokolade, Marzipan, Zucker, Fruchtsaft, Marmelade, Gelee usw

Ohne Zusammenfassung     

Finite-size effects in the self-organized critical forest-fire model

We study finite-size effects in the self-organized critical forest-fire model by numerically evaluating the tree density and the fire size distribution. The results show that this model does not display the finite-size scaling seen in conventional critical systems. Rather, the system is composed of relatively homogeneous patches of different tree densities, leading to two qualitatively different types of fires: those that span an entire patch and those that do not. As the system size becomes smaller, the system contains less patches, and finally becomes homogeneous, with large density fluctuations in time. Received 24 April 1999 and Received in final form 26 October 1999     

Deposition and Characterization of Metastable Cu3N Layers for Applications in Optical Data Storage

 Cu₃N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For basic investigations concerning the composition and structure of Cu₃N, Si wafers were used as substrate material. To study the suitability of Cu₃N as an optical data storage medium under technical conditions, Cu₃N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The decomposition of Cu₃N into metallic copper and nitrogen was induced and characterized with a dynamic tester consisting of an optical microscope with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity photo detector. Optimized Cu₃N films could be decomposed into metallic copper at pulse lengths of 200 ns. The reflectivity change from 3.2% to 33.2% for completely transformed areas and to 12% for single bits as well as the maximum write data rate of 3.3 Mbit/s demonstrated the suitability of Cu₃N for write once optical data storage. Especially the carrier to noise ratio of 41 dB shows an increase of a factor of 3 for this novel material as compared to conventional optical data storage media.     

Nickel and palladium complexes of enolatefunctionalised N-heterocyclic carbenes

The reaction of chloroethyltrimethylsilylether with 1-methylimidazole furnishes an ionic liquid that undergoes methanolysis to crystalline 2-hydroxyethylimidazolium chloride (crystal structure presented). Conversion to defined hydroxyethylimidazol-2-ylidene nickel complexes failed, but was accomplished with 1-methyl-3-acetophenyl-imidazolium bromide. The bis(NHC^⋂O⁻) nickel(II) chelate is formed, rather than a methallylnickel monochelate, but with nickelocene a monochelate NiCp complex was detected. The bulky 1-(2,6-diisopropylphenyl)-3-(2’-phenyl-enolato)-imidazol-2-ylidene allylpalladium chloride was obtained in pure form. Attempts to generate catalysts for ethylene oligomerization by in situ techniques have failed so far whereas P^⋂O⁻ ligands, comparable by the P-C diagonal relationship, provide active catalysts.      

Ethanol/water solutions as certified reference materials for breath alcohol analyzer calibration

The Federal Institute for Materials Research and Testing (BAM), Germany, has issued a series of large volume ethanol in water certified reference materials (CRMs), primarily developed for the calibration of evidential breath alcohol analyzers in Germany. The certified parameter is the ethanol mass concentration at 20 °C. When used in a wet bath simulator, the solutions deliver gas samples that meet the requirements set by the Organization of Legal Metrology for calibration of breathalyzers. The materials were prepared gravimetrically by spiking of ethanol into water in single 5 L units. A complete uncertainty budget for the preparation process has been established. The purity of the commercial ethanol stock solution was identified to be the main source of uncertainty. For stability and homogeneity measurements and for the verification of the gravimetric mass concentration of the CRMs, a robust high-precision gas chromatography, with flame-ionization detection method for ethanol determination in aqueous samples was developed and validated. The good performance of this method has been demonstrated in several international comparisons organized by the Consultative Committee for Amount of Substance—Metrology in Chemistry at the International Bureau of Weights and Measures.     

Modelling and Simulation of solidification processes in polymer melt flows

This work deals with the modelling and simulation of solidification processes in polymer melt flows. Two models describing the latent heat and the rheological behaviour were implemented in a finite volume code. The models are empirical and their parameters are identified using experimental results obtained from investigations with a rotational rheometer and a differential scanning calorimetry. First results of the simulation of a solidifying channel flow are shown. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)