A phenomenological theory of the isotropic to chiral smectic-C phase transition

In this paper we discuss the direct isotropic to chiral smectic-C phase transition on the basis of a phenomenological theory. The model free energy is written in terms of the coupled order parameters including the spontaneous polarization. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions a direct isotropic to chiral smectic-C phase transition is possible when compared to other phase transitions. On the basis of this model the isotropic-smectic-C^* transition is always of first order. The theoretical predictions are compared with the available experimental results.-1     

Hydrodynamics of nematic ferrofluids

The European Physical Journal E - We derive hydrodynamic equations for nematic ferrofluids (ferronematics) in the limit that the magnetic degree of freedom has relaxed to its equilibrium value. We...     

The synthesis and characterisation of an expansive additive for M-type cements

The expansion effect of laboratory-prepared expansive additives for M-type expansive cement was investigated at the early stage of hydration by the multicell isoperibolic calorimeter and volumetric technique based on Archimedes’ principle. The relative volume changes and heat released during hydration are strongly affected by the content of lime in the expansive additive due to the influence of CaO on the kinetics and mechanism of formation of ettringite. The increasing content of lime favours the formation of monosulphate and its later transformation to ettringite generating expansion stress. The effect of expansive additive on the behaviour of mortar samples was measured as linear elongation of test blocks using Graf-Kaufman dilatometer. Lower or higher content of lime in expansion additive slightly decreases the 7th-day compressive and flexural strength of samples while this effect is negligible for expansive additive with nominal composition of ettringite.     

Zur Existenz des Oxoniumions in festen basischen Aluminiumsulfaten

On the Existence of the Oxonium Ion in Solid Basic Aluminium Sulphates Oxonium alunite was investigated by ¹H-NMR-, heat capacity, electric conductivity, and thermoanalytic measurements. In the ¹H-NMR spectrum the existence of the oxonium ion was surely proved. From the results of the other investigations follow, that the oxonium ion is fast bonded in the structure and that exists an unimportant amount of mobile ionic charge carriers only.