Many-cluster-systems: models of inhomogeneous matter

First, some general remarks concerning macroscopic “cluster matter” are given. In the second part, three recent, mainly optically and electron-microscopically performed investigations are discussed which deal with special properties of noble metal cluster systems forming the building units of this kind of matter:(1) dressed Au-55 clusters,(2) electromagnetic coupling effects among coagulated clusters,(3) the transition towards compact inhomogeneous matter caused by coalescence of clusters.     

Buchbesprechungen

Ohne Zusammenfassung     

Stationary policies and Markov policies in Borel dynamic programming

Summary The question of the existence of good Markov [good stationary] policies is studied for a general class of Borel [stationary] dynamic programming models. It is shown, for example, that Markov [stationary] policies are uniformly adequate if every transition law is absolutely continuous with respect to a fixed measure [and the reward function is positive or the model satisfies certain compactness and continuity conditions].Research supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 72Research supported by National Science Foundation Grant MCS 8100789     

Fast proton conductivity of polycrystalline titanoniobates

The proton conductivity of three layer-type compounds was studied: H₃OTi₂NbO₇. H₂O, HTiNbO₅ and HTiTaO₅. Measurements were made between 20 °C and 90°C on pellets pressed from crystalline powders and soaked with pure water. The hydrated compound had the highest conductivity, (20°C)-6.3–6.9·10^–4 (cm)^–1. Acid ions from the exchange process were quite firmly retained in its layer structure and contributed significantly to the measured conductivity. Consistent results were obtained after prolonged washing with water.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Zur reaktionsweise von triafulvenen mit azomethinyliden

The reaction of the azomethine ylides 2a–c with cyclopropenones 3 and of 2a with methylene cyclopropenes 7 leads via (3+3)-cycloaddition to pyridones-4 5 and 1,4 - dihydro - N - methyl - 4 - methylene - pyridines 8, respectively. The merocyanine systems 8 exhibit marked solvatochromic and thermochromic properties.