Objective comparison of concentration profiles in solids by means of mathematical statistics

To compare concentration profiles in solids in an objective manner, a multi-dimensional generalization of the comparison of two means by Student'st-test is proposed. The approach is based on piecewise modelling the profiles using rougha priori information, estimating the model parameters and their covariance matrix and comparing the estimated parameters by use of multidimensional test variables. The piecewise modelling is treated in the most important cases in such a way that the partial functions are straight lines or cubic polynoms (splines) with continuity at all knots in each case. It enables us to compare whole profiles as well as the most relevant parts of them. Two ways of estimating the covariance matrix as a generalization of the variance estimation are discussed. The approach is useful for any kind of line profiles if rough information on the profile type is available. As an example SIMS depth-profiles of aluminum obtained from thin-layer systems after different technological heat treatments are considered. These profiles are modeled by three straight lines.     

An improved system for data acquisition and analysis for viscoelastic measurements of dilute macromolecular solutions with the modified birnboim-schrag multiple lumped resonator

A new system of data acquisition and analysis has been developed for the modified Birnboim-Schrag multiple lumped resonator apparatus which is used to measure the viscoelastic properties of long-chain macromolecules in dilute solution. The modifications to the original apparatus include improved temperature control and vibration isolation. The original theory has been reworked so that each resonance mode can be characterized by a greater number of data points. The entire data acquistion/processing system is automated and placed under computer control; a correlation for mode coupling is derived. The modifications result in improved precision in the measured viscoelastic moduli and increased instrumental reliability.     

Transferreaktionen mit Hilfe von Pb(OAc)4−n (N3) n 1, 7. Mitt.: Zur Reaktivität der Dreifachbindung

Zusammenfassung Das Verhalten von Diphenylacetylen, Phenylacetylen und 1-Phenyl-2-trimethylsilylacetylen gegenüber dem System Pb(OAc)₄–(CH₃)₃SiN₃ bei –20° läßt sich so interpretieren, als ob positives Azid transferiert würde. Bei Raumtemp. kann auch ein radikalischer Reaktionsablauf in Erwägung gezogen werden.

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Transfer reactions with Pb(OAc)_4–n(N₃)_n (the reactivity of triple bonds, VII)

The behaviour of diphenylacetylene, phenylacetylene and 1-phenyl-2-trimethylsilylacetylene against the mixture Pb(OAc)₄–(CH₃)₃SiN₃ can be interpreted at –20°C, by a transfer of formally positive azide. At room-temperature a radical mechanismus can be involved too.

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Herrn Prof. Dr.L. Horner (Universität Mainz) zum 60. Geburtstag in aufrichtiger Verbundenheit.     

Quantitative X-ray diffraction analysis of textured sheet metals

A disadvantage of the quantitative X-ray diffraction analysis of samples from sheet metals is the incorrectness of the measuring results owing to the presence of textures in the material. In considering several reflexes of every phase the influence of textures may be reduced. Such a method will be presented and tested. The yielded results show that the new method can be useful for textured sheet metal samples.     

Symmetry adapted harmonic oscillator functions

Quantum mechanical excited energy states of two- or three-dimensional harmonic oscillators are highly degenerate. A general method is presented to calculate the symmetry adapted quantum mechanical oscillator functions with respect to the symmetry group of the oscillator. In the special case of the tetrahedral symmetry group the method is demonstrated by detailed formulas for the two- and three-dimensional case. A computer program is also available. The method can easily be modified for other symmetry groups.     

Stereoselective Ring Opening of Electronically Excited Cyclohexa-2, 4-dienones: Cause and effect

The two conformers of a cyclohexa-2, 4-dienone with different substituents at C(6) on irradiation are believed to undergo ring opening stereospecifically affording a mixture of two configurationally isomeric diene-ketenes (and descendents thereof)- Exceptions are generally found for those dienones with one C and one O substituent or even with two C substituents, if one of them carries a polar group at a site able to interact through space with the ring C?O group. In these cases, only one of the two anticipated diene-ketenes (and descendents thereof) is produced. A thorough investigation of the photochemistry of a series of structurally different cyclohexa-2, 4-dienones on analytical as well as on preparative scale extends our mechanistic knowledge of the various routes from diene-ketenes into a variety of compound classes. Novel compound classes accessible to diene-ketenes are seven-membered carbocycles (by intramolecular aldolization of the zwitterion of appropriately substituted, transiently formed diene-(N, O)-ketene acetals) and β-lactams (by Staudinger reaction).     

The Suitability and Usage of 18O and Chloride as Natural Tracers for Bank Filtrate at the Middle River Elbe

Abstract

Flow times and infiltration behaviour are very important for water extraction from riverbank filtration. Both the chloride content and the isotopic composition of oxygen (δ¹⁸O) were found to be suitable indicators for the conditions encountered in the middle course of the River Elbe near Torgau. The ranges for Elbe water were measured to be 20–43 mg Cl/l (1995-97) and -11 to -8.5‰ δ¹⁸O (1993-97). Both methods permitted flow-time spectra at two adjacent sampling profiles incorporating river and production wells to be obtained, indicating the preferred flow paths and the vertical extension of the riverbank filtrate plume in the aquifer. However, since the differences between the mean values for river water and regional groundwater were too small the percentage of river water abstracted from production wells could not be calculated.