Comparison of packed and capillary columns for practical SFC separations

Summary A newly developed polysiloxane-type packing material shows promise for use in SFC. Relatively polar compounds were eluted from a microbore column with good peakshape using a mobile phase consisting of CO₂ modified with formic acid and water. The latter combination is an effective modifier suitable for use with pressure programming and FID detection.

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Vergleich von gepackten und Capillar-Säulen für praktische SFC-Trennungen

     

No minimally reasonable collective-choice process can be strategy-proof

In this paper I will prove that every collective-choice process fulfilling certain mild requirements - notably a version of Nondictatorship and a very weak unanimity-reduction condition - is manipulable: none is strategy-proof. Gibbard and Satterthwaite have each proved a similar result just for resolute processes - ones yielding only single-member choice sets. My theorem does not assume resoluteness, which I criticize as an unreasonable requirement.     

Investigations on surface diffusion in sparingly soluble monolayers at the gas/liquid interface using radiotracer technique

Summary For creating favourable conditions for the experimental proof of surface-diffusion processes in sparingly soluble monolayers at the gas/liquid interface by means of radiotracer technique, possible factors of influence such as evaporation, desorption and convection were studied. From radiotracer measurements it followed that the share of evaporation and desorption in case of long-chained n-alkanols and n-alkane-carboxylic acids can be neglected. Even at correct experimental setup long-term movements of monolayer material occurred which, on the one hand, induced a lateral shifting of the boundary labelled/non-labelled, on the other a wavelike distribution of the monolayer material which initially had a statistically homogeneous distribution. The analysis of possible mechanical and thermal causes showed that these phenomena can be explained only by temperature-induced density instability in the volume phase of the trough. On this basis a model is proposed which explains the formation of compressed and expanded areas of monolayer material.

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Zusammenfassung Zur Schaffung günstiger Bedingungen für den experimentellen Nachweis von Oberflächendiffusionsvorgängen in schwerlöslichen Monoschichten an der Phasengrenze Gas/Flüssigkeit mit Hilfe der Radiotracertechnik wurden mögliche Einfluggrößen, wie Verdampfung, Desorption und Konvektion, untersucht. Aus Radiotracermessungen resultierte, dag der Anteil von Verdampfung und Desorption bei langkettigenn-Alkanolen undn-Alkansäuren vernachlässigt werden kann. Auch bei einwandfreier Versuchsdurchführung traten langzeitige Bewegungen des Monoschichtmaterials auf, die einmal zur lateralen Verschiebung der Grenze markiert/nichtmarkiert, zum anderen zur wellenförmigen Umverteilung des anfangs statistisch homogen verteilten Monoschichtmaterials führten. Die Analyse möglicher mechanischer und thermischer Ursachen ergab, daß diese Erscheinungen nur durch temperaturbedingte Dichteinstabilität in der Volumenphase des Troges erklärt werden können. Auf dieser Basis wird ein Modell vorgeschlagen, das die Ausbildung komprimierter und expandierter Bereiche des Monoschichtmaterials erklärt.

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With 6 figures and 1 table     

Sur la structure des algèbres de Kac,I

We elaborate on the relative situation of a Kac algebra and its dual, then, introducing three invariants we obtain a generalization of Heisenberg's commutation relations. Using the operator-valued weights introduced by U. Haagerup, we give a simpler definition for Kac algebras. As an application, we generalize the unicity of the left Haar measure on a locally compact group.