Ein Kriterium für das Fehlen von Eigenwerten elliptischer Differentialoperatoren

Ohne Zusammenfassung     

Über die symmetrie elliptischer differentialoperatoren

Ohne Zusammenfassung     

Sign inversion of the helical pitch in carbohydrate-based liquid crystals

A four-step synthesis starting from tri-O-acetyl-D-glucal leads to chiral trioxadecalin compounds containing a cyano group. The mesogenic properties of a homologous series of liquid crystals are reported; for two derivatives a helix inversion of the cholesteric phase is observed.     

Regularitätsaussagen mit Anwendungen auf die Spektraltheorie elliptischer Differentialoperatoren

Ohne Zusammenfassung     

Zur Verallgemeinerung des Nevanlinnaschen Defektbegriffes durch Dinghas

Ohne Zusammenfassung     

Cholesteric helix inversion: Novel nitro compounds showing unusual changes of the cholesteric helical pitch

We present a homologeous series of liquid crystalline trioxadecalin compounds having a terminal alkoxy chain and a nitro group. The (1S, 3R, 6R,8R)-3-(4'-nitrophenyl)-8-(4'-octoxyphenyl)-2,4, 7-trioxabicyclo [4.4.0]decane 2 c shows a temperature-dependent inversion of the cholesteric helix at lower temperatures. For higher temperatures, the reciprocal helical pitch reaches a minimum, then it increases, tending to a second inversion point just above the clearing point. An additional chiral centre in the side chain leads for nitro compounds 3 to non-mesomorphic behaviour. For the cyano compounds 4, the change in the cholesteric helix is suppressed, for the R configuration, but for the S configuration helical inversion occurs at high temperatures and selective reflection above the transition to the TGB_A phase.     

Kriterien zur selbstadjungiertheit elliptischer differentialopemtoren I

Ohne Zusammenfassung Vorgelegt von L. Collatz Die vorliegende (zweiteilige) Abhandlung ist eine Überarbeitung der Habilitationsschrift des Verfassers.     

Ein Regularitätssatz zur schwachen 2. Randbedingung mit Anwendungen auf elliptische Differentialoperatoren

Ohne Zusammenfassung     

Re-entrant and induced mesophases: Mixed systems showing re-entrant TGBA and re-entrant cholesteric phases

We have investigated the behaviour of chiral carbohydrate-based trioxadecalines with a cyano group in mixed systems. The mixture of a trioxadecaline having a Ch phase and a trioxadecaline having a Ch, S_A and a S*_Cphase sequence induces a re-entrant TGB_A and Ch phase. Below the stabilized S*_C phase, a re-entrant Ch phase is observed. In the mixture of the cholesteric trioxadecaline with CCH7, itself only showing a nematic phase, a TGB_A phase and a broad range S_A phase are induced from two non-smectic compounds. Both mixtures show a blue phase with a pitch ranging from the UV to red depending on the molar fraction.