Über Abkömmlinge der Nitrohemipinsäure

Ohne Zusammenfassung     

Boundary sets where harmonic functions may become infinite

This paper characterizes the subsets E of which have the following property: there exists a harmonic function u on such that as for each x inE. This problem has its roots in classical work of Lusin and Privalov, and the answer has been known for some time in the case where n=1. However, the characterization turns out to be more delicate in higher dimensions. Received: 19 March 2000 / Published online: 1 February 2002     

(1 1 0) oriented quantum wells and modulation-doped heterostructures for cleaved edge overgrowth

The dependence of the optical quality, i.e. the line width and homogeneity of (1 1 0) oriented quantum wells on the substrate temperature, the As pressure as well as on the As species is studied by means of micro-photoluminescence. Molecular beam epitaxial growth using the As dimer leads to a photoluminescence line width as narrow as 5.5 meV for 7 nm wide quantum wells compared to a value of 8 meV for the As tetramer source. In addition to the small line widths which can be achieved using As , quantum wells grown under these conditions are also superior to those using As in terms of uniformity on a m length scale. In contrast, the peak mobility of a two-dimensional electron system located at a (1 1 0) oriented GaAs/AlGaAs heterointerface of cm V s is obtained for tetramer growth, while the use of As degrades the electron mobility to values below 500 000 cm V s.     

Determination of trace elements in organic material by inductively coupled plasma-mass spectrometry

Summary For purposes of trace element analysis of organic materials a combined analytical procedure is tested. It consists of a pressure decomposition by nitric acid at 220° C in quartz vessels. The measurements are performed in the diluted digests by inductively coupled plasma/mass spectrometry. Analytical figures of merit are given.Dedicated to Prof. Dr. Karl Winsauer on the occasion of his 60th birthday.     

Scanning electron microscopy studies on surfaces from electrothermal atomic absorption spectrometry—I: Polycrystalline electrographite tubes with and without pyrographite coating

Morphological studies on graphite tube surfaces by scanning electron microscopy are presented for unused and corroded tubes from various endurance experiments in electrothermal AAS.Tubes always break in their center as this is the hottest part; tube thinning occurs predominantly at the outside. The inner surface of tubes coated with pyrographite is usually only slightly corroded, unless highly aggressive reagents are applied. Deposition of carbon in thin layers as well as in nodules is observed in the hot central zone.