A microcomputer for the simultaneous data processing of different automatic elemental analysers

Summary A microcomputer has been developed for automated data processing of different automatic elemental analysers. The microcomputer allows users, already in possession of multimeters or integrators, an electronic microbalance and elemental analysers, to combine their equipment into an automated system. Depending on the elemental analysers available, it is possible with this system to determine simultaneously the elements C-H-N and O, C-H-N and S, or O and S, or it is also possible to determine these elements in duplicate. The microcomputer system is flexible and can easily be adapted for other applications by changing the software. After the analysers have been started, this system processes all data and calculates the blanks, calibration factors and percentages successively. The modes of operation of the principal parts of the microcomputer are described.

---

Ein Mikrocomputer zur gleichzeitigen Datenverarbeitung verschiedener automatischer Elementaranalysengeräte

Zusammenfassung Ein Mikrocomputer zur automatischen Datenverarbeitung verschiedener automatischer Elementaranalysengeräte wurde entwickelt. Dieser ermöglicht, Vielfachmeßgeräte oder Zählgeräte, eine elektronische Mikrowaage und Analysengeräte zu einem automatischen System zusammenzuschließen. Je nach dem vorhandenen Analysator lassen sich damit C-H-N und O, C-H-N und S oder O und S gleichzeitig bestimmen oder man kann Doppelbestimmungen dieser Elemente durchführen. Das Mikrocomputer-System ist flexibel und kann durch Austausch der Soft-ware leicht für andere Zwecke adaptiert werden. Nach dem Start der Analysatoren verarbeitet dieses System alle Daten und berechnet die Leer werte, die Berechnungsfaktoren und die Prozentgehalte der Reihe nach. Die Arbeitsweise der Hauptteile des Mikrocomputers wurde beschrieben.

     

Silver whiskers and epitaxial layers on tungsten tips as fem specimens; Their growth and behaviour on annealing and oxidation

In order to investigate whether field-emission microscopy (FEM) can be applied to the examination of adsorption on low-melting metals, a study has been made of the preparation and the stabilization of silver surfaces that are suitable as field electron emitters. Single silver whiskers, showing negligibly distorted FEM patterns, could be grown at 873 K by in-situ deposition of silver vapour onto the apex of thermally cleaned blunt tungsten tips. Single-crystal silver layers could be grown at 296 K by the same technique on field-evaporated sharp tungsten tips. The nucleation and growth of the layers take place more uniformly on these crystallographically perfect surfaces than on thermally cleaned tips. At elevated temperatures (673 K) considerable diffusion of silver from the apex of the tip to the shank was noticed when the latter had been thoroughly cleaned by previous heating. The occurrence of this effect was avoided by applying the field-evaporation step in the tip-preparation procedure after the tip had been strongly oxidized ; thus, the oxidized tungsten bordering the cleaned apex acts as a silver diffusion barrier. The silver surfaces obtained have a high degree of cleanliness. Adsorbed oxygen can easily be removed by heating to 673 K ; hardly any blunting results from this treatment. However, when a silver layer has been strongly oxidized, complete field desorption of silver reveals oxidation also of the tungsten at the tungsten-silver interface. Application of positive voltages to a crystalline silver layer on a tungsten tip at 77 K in ultra-high vacuum deforms the layer extensively before actual field evaporation of silver is achieved.     

Electric field effects in 13C NMR of some quaternary morphinan derivatives

¹³C NMR chemical shifts are assigned for some quaternary morphinan derivatives, including the ‘minor isomer’ of the thebaine N-oxides. In quaternary morphinan alkaloids having an 8.14-double bond, electric field effects cause unusual ¹³C NMR shifts.     

Pattern measurements of a low-sidelobe horn antenna

The power pattern of a corrugated horn antenna designed for low sidelobes was measured to levels 90 dB below the main beam maximum in both theE- andH-planes. The measured patterns were found to be in good agreement with theoretical predictions.     

Verbesserte Mikroborbestimmung im Picogramm-Bereich bei Gegenwart der Eisenmetalle

Ohne Zusammenfassung

---

Improved microdetermination of boron in the picogram range in presence of the iron metals

---

Wit danken der Deutschen Forschungsgemeinschaft sowie dem Landesamt für Forschung des Landes Nordrhein-Westfalen für Sachbeihilfen und den Herren stud. chem. U. Schinke und stud. chem. R. Langenberg für ihre sorgfältige Mitarbeit.     

Bifurcations with nonuniversal exponents in a lattice model

The bifurcations of a two-dimensional area preserving mapping with a cubic term are studied. This mapping shows a large number of bifurcations where the period becomes a multiple. For a given order of bifurcation exponents are found which depend on the series considered. The exponents calculated numerically are compared with renormalisation calculations for a number of cases.