Bifurcations in a Bistable Reaction-Diffusion System

The bifurcations of stationary solutions of bistable reaction-diffusion systems and especially the model due to Schlögl are investigated. The paper is based on the observation that these dynamical systems belong to the gradient type, i.e. methods of topological investigation of the corresponding potential may be applied. Three different types of models are discussed: 1. Homogeneous model; 2. Compartmental model with diffusion; 3. Continuous model with diffusion. Bifurcation maps and relations to catastrophe theory are given.     

Messungen zum lateralen Auflösungsvermögen für Röntgenquanten bei der Elektronenstrahl-Mikroanalyse

Zusammenfassung Die experimentelle Bestimmung der lateralen Ausdehnung des Röntgenemissionsvolumens gelingt aus Intensitätsmessungen an Schichten, deren Dicken in der Größenordnung der lateralen Ausdehnung liegen. Die Schichtsysteme werden dabei mit definierter Geschwindigkeit unter dem Elektronenstrahl hinweg bewegt, was einem Wandern des Röntgenemissionsvolumens durch das Schichtsystem gleichkommt. Von einer Schicht, deren Röntgenintensität gerade das Maximum eines Reinelement-Massivstandards erreicht, kann angenommen werden, daß ihre Dicke der lateralen Ausdehnung entspricht. Zur Messung der Schichtdicken wurden in erster Linie Liniendiagramme herangezogen; die Überprüfung erfolgte aus Röntgenrasterbildern der Elementverteilung.Die geeignete Auswahl der Proben, die aus Schichten leichter (Kohlenstoff), mittlerer (Kupfer) und schwerer (Gold) Elemente bestehen, gestattete die Interpolation der Ergebnisse auf Elemente beliebiger Ordnungszahl. Die Messung der Röntgenintensitäten bei verschiedener Anregungsenergie des Elektronenstrahls ergibt die Abhängigkeit der lateralen Ausdehnung von der Beschleunigungs-spannung.

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Measurements of the lateral resolution of X-ray emission by means of electron microprobe analysis

Summary The experimental determination of the diameter of the X-ray emission volume is obtained from intensity measurements on layers whose thickness lie in the range of this emission volume. The vertically orientated sandwich layers were moved with a definite velocity under the electron probe which amounts to a wandering of the X-ray emission volume through this system of layers. From a layer whose X-ray intensity is equivalent to maximum intensity of a bulk standard of the same material as the layer, one can assume that the diameter of the X-ray emission volume corresponds to the thickness of the layer. To measure the layer thickness, mostly linescans were used, followed by X-ray scan pictures of the element distribution to verify the same.A suitable choice of samples representing light (carbon), medium (copper) and heavy (gold) elements enables to interpolate the results on elements of any other mass number. The measurement of the X-ray intensity under varying electron energies shows the dependance of the diameter of the X-ray emission volume on accelerating voltage.

     

Distinction between glycosylamines and amadori products by mass spectrometry of their trimethylsilyl derivatives

The TMS-ethers of four glycosylamines and seven Amadori compounds have been investigated by electron impact mass spectrometry. The mass spectra of glycosylamine-TMS derivatives and of their isomeric Amadori rearrangement products are quite characteristic. The two types of compounds can be distinguished by a few characteristic peaks.     

Mehrsortige Logische Systeme mit Unendlich langen Formeln II

Ohne ZusammenfassungHerrn Professor Dr. Kurt Schütte zum 60. Geburtstag gewidmet.Es handelt sich um eine Fortsetzung von Teil I in Band 14, pp. 38–53 dieser Zeitschrift. Literaturhinweise beziehen sich auf das Literaturverzeichnis am Ende von Teil I.     

Eine Methode zur Bestimmung der spezifischen Radioaktivität der „freien Aminosäuren“ in Gewebeextrakten von Säugetieren

Some experiences are given with a measuring device for the determination of the specific radioactivity of ¹⁴C-labelled brain amino-acids. The apparatus consists of an automatic amino-acid analyzer combined with a flow cell filled with anthracene. The reproducibility of the method is ±5% to ±1% m.e. in the range of 1×10^?3 μCi to 5×10^?2 μCi. A quantitative determination of 3×10^?4 μCi/ml eluant is still possible.     

Der Zusammenhang zwischen dem magnetooptischen Kerr- und Faraday-Effekt und die optischen Konstanten von dicken Aufdampfschichten aus Eisen,Kobalt und Nickel

The magnetical rotation of the plane of polarisation and the ellipticity of the reflected and transmitted light through magnetically saturated, evaporated layers of iron, cobalt and nickel (30 to 100 mμ) are dependent one another according to the phenomenological theory of W.Voigt. The four measured magnetooptical angles are however independent each other. By comparison of other physical properties, except the magnetooptical ones, (f. e. magnetical saturation, optical absorption) measured respectively with transmitted and with reflected light, we try to prove, that the layers are homogenous at least near the glass-side. The linear increase of Faraday-rotation and optical absorption with the thickness of the layer supports this assumption. Then the independence can only be explaned by a magnetooptical term in the second equation of Maxwell also (precession of spin). The knowledge of the optical constants ist necessary for the comparison of magnetooptical ones. They are find out by measurements of intensity only, using the transmitted light and the reflected light at both sides of the layer. By supernumerarykinds of determination the foult is estimated. The method of Drude is adapted to measurements of intensity and then applied on the glasside too. The results on this side agree with those of transmitted light, the air-side differs a little.     

Quasimolecular nuclear optical potentials

A theory is presented to calculate potentials for the elastic nuclear heavy-ion scattering in a phenomenological way. The density properties of finite nuclei are derived with a schematic ansatz for the interaction energy between nuclear matter. The same interaction energy is applied to the calculation of the real part of the heavy-ion potential, which is of the quasimolecular type. The imaginary part is connected with the outflow time of nuclear matter out of compressed regions of overlapping nuclei. The resulting cross section for the elastic O¹⁶-O¹⁶ scattering reproduces the experiment up to 30 MeV quite well. An effective compression modulus of the S³² compound system can be deduced from the scattering experiment. It results to be about 200 MeV.