ET-AAS determination of traces of As, Sb and Sn in pure gold after matrix separation with hydrazine

Summary The possibilities of ET-AAS using the graphite furnace or the tungsten coil atomizer were compared by the trace As, Sb and Sn determination in the chloride-containing solution resulting after gold reduction with hydrazine. It was found that the tungsten coil atomizer tolerates higher concentrations of chloride ions than the conventional graphite furnace.     

Determination of traces of sulphur by electrothermal evaporation and non-thermal excitation of S-containing species in a hollow cathode discharge (FANES/MONES) and in a microwave induced plasma (MIP)

Summary The determination of sulphur by emission of S-atoms, S⁺ ions, S₂ and CS molecules using sulphate and other ions was investigated in such non-thermal excitation sources as the normal atmospheric argon-MIP and glow discharge in FANES/MONES (Furnace Nonthermal Excitation Spectrometry/Molecular Nonthermal Excitation Spectrometry). In both cases electrothermal evaporation (ETE) of the sample is applied. In the MIP technique (ETE-MIP) electrothermal evaporation from a new tungsten coil system is used and in the FANES samples are brought in the furnace. The thermal, electrical, chemical and pressure conditions were optimized and the emission spectra recorded. Detection limits are 90 ng for the ETE-MIP technique using the S 469.413 nm atom line. With the tungsten tube-FANES/MONES detection limits of 17 ng are obtained with S₂ molecular band at 383.73 nm. With FANES/MONES in a carbon tube and measurements on CS molecular bands a detection limit of 2 ng is obtained.Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Beschreibung des inneren Spannungszustandes von Polyester-Faserstoffen durch Messung der Gleichgewichtsschrumpfkraft

Zusammenfassung Es wird eine modifizierte Schrumpfkraft-Meßmethode, die sog. Gleichgewichtsschrumpfkraft-Messung, vorgestellt, die sich besonders informativ und schnell zur vollständigen Beschreibung des inneren Spannungszustandes von Fasern und Garnen eignet. An zwei praktischen Beispielen aus dem Bereich der Struktur-Eigenschafts-Beziehungen von PES-Fasern werden einige mit dieser neuen Meßtechnik gewonnene Versuchsergebnisse diskutiert.Eine Automatisierung des Meßablaufes ist durchaus möglich, was z. Z. realisiert wird.

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Summary The properties of textiles from PET fibres are decisively depending on the stresses set within the material. According to the thermal stability of molecular interactions these stresses can be released by thermal treatments at different temperatures. As a consequence of stress release the material shrinks. Informations on the stresses built in can be achieved by following up the development of contraction force (shrinkage force) as a function of temperature when heating the fibres under constant length. By variation of heating rates retarded stress development and stress relaxation are observed. In this case the real set tensions due to prior treatments are not recorded.A new modified technique of measuring shrinkage forces provides in certain intervals of temperature an alteration of the clamped lengths by a minute stretching or shrinking of the fibres in a manner resulting a zero force deviation. So at each temperature we have an equilibrium of the released inherent stresses of the fibres and the recorded ones. These socalled equilibrium-shrinkage-force-curves are capable of describing the state of order of PET-fibres in a better way than other methods do. It will be shown that the formerly developed parameters of a heat treatment effective temperature and effective tension (8) can be derived from these curves as well as those tensions which had been set up in the fibres during cooling and processing or relaxed during storage.

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Herrn Prof. Dr.G. Rehage zum 60. Geburtstag gewidmet.

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Mit 9 Abbildungen     

Signal summation for the improvement of the detection performance and indirect increase of the sample quantity in direct AAS of solids

Summary Time-resolved AAS signals of several, individually-weighed, solid samples were stored and later summed by the personal computer. This summation yields a signal covering all the individual samples, with a signal-to-noise ratio which is improved according to the law familiar from other replicate determination techniques. This makes it possible to determine concentrations in samples at levels where it would otherwise be necessary to resort, for instance, to a preliminary chemical concentration step. The technique has been applied to the determination of traces of Pb and Cd in malt and yeast.     

Perspectives of data-flow architectures

For about forty years now, computer architecture design has followed the Von Neumann principles. By added features, e.g. pipelined processor organisation, vector/array-processing, multiprocessing and today's technology we are looking at supercomputer designs, which may have scalar performance of several hundred Mflops and vector performance of thousands of Mflops but the design space of Von Neumann-type computers seems to be exploited and hardware technology is assumed to reach a point at which physical constraints limit further performance improvements.Therefore, it is growingly accepted that non-Von Neumann models of computation are necessary to exploit program concurrency. A highly promising part of current research on concurrent computer organisation is focused on two principles, which are distinguished by the way computations manipulate their arguments and by the way the execution of computations is initiated: Pure data-driven schemes and schemes which combine data-driven and demand-driven computation.Both schemes seem suited to support a project Guiding Land Vehicles along Roadways by Computer Vision.     

Über eine zum Kreisproblem verwandte Summe II

Let β, γ,x∈? with β>1, 0<γ<1/β and χ>0, a large variable. Furthermore, letψ _k denote the lperiodic Bernoulli polynomial of orderk∈?(k?2). If β>2 then it is known [2] that $$\sum\limits_{n \leqslant (x/2)^{1/\beta } } {\psi _k ((x - n^\beta )^\gamma )} = O(x^{(1 - \gamma )/\beta } )$$ . The aim of this note is to show that the exponent (1?γ)/β is best possible by determining a principal term in the asymptotic expansion of the l.h.s. of (*). Moreover, this result still remains valid even in the case 1<β≦2, but with a slight restriction for γ.