Joanna Janik

Dielectric studies of the 4-n-alkyl-4'-thiocyanatobiphenyl (nBT) homologous series (n=2-10) in the isotropic and E phases

Results of the dielectric studies of nine members of the nBT (4-n-alkyl-4-thiocyanatobiphenyl, n= 2-10) homologous series in the crystal E (E) and isotropic (I) phases are presented. The dependence of the static permittivity εs in the isotropic phase, the longitudinal relaxation times τis and τ∥, and the activation enthalpies ΔH is and ΔH ∥ on the number of carbon atoms in the alkyl chain n are analysed. A considerable increase in the retardation factor g= τ∥/τis with decreasing n is observed. The results are compared with those obtained for similar two-ring homologous series. The parameters characterizing the molecular rotations around the short axis in the E phase (τ∥ and ΔH ∥) indicate a hardening of this solid-like phase with shortening of the alkyl chain.

Phase transition and dielectric studies of a three-ring homologous series with the -NCS terminal group

The synthesis route and phase properties for a new three-ring homologous series, 4-(trans,trans-4-alkylbicyclohexyl)benzene-isothiocyanates (nCCHBT) with n=2-7, are presented. The substances exhibit very broad range nematic phases exceeding 200 K, and low viscosity with a low activation enthalpy. The dielectric properties of the nCCHBT materials are compared with those of their long known two-ring analogues (nCHBT). The static permittivity, epsilons is considerably lower for the three-ring compounds. It is found that epsilons decreases with n at temperatures as low as Tr=T/TNI=0.7. The relaxation time, tau shows the odd-even effect, the amplitude of which reverses on going from Tr=0.7 to 1. The activation enthalpy for molecular rotation about the short axis alternates with n practically in the same manner for the corresponding members of both homologous series. It is argued that the present results are at odds with models assuming that the activation enthalpy consists of the viscosity and nematic potentia...

Improved Miesowicz Viscometer

Abstract The main features of the Miesowicz torsionai viscometer with automatized detection of the plate movement are described. An application of the viscometer to study the anisotropy of viscosity in nematic mixtures RALLE5 and WARSAW4 is shown as an example.

Pendulum viscometer: A new method for measurement of Miȩsowicz nematic shear viscosity coefficients η1 and η2

We describe a new viscometer developed for liquid crystals. It has been designed for measurement of the Miesowicz viscosity coefficient η2 (n‖v) in particular, but can be used for measuring η1 (n‖∇v) as well. The measurement is based on observation of the damped motion of a pendulum and derivation of the viscosity coefficient from the damping constant.

Detailed study of a two component smectic 4TPB–8OCB system with a nematic gap. Phase diagram and viscosity study

Abstract The phase diagram of a two component system composed of two smectic compounds: 4-octyloxy-4′-cyanobiphenyl (8OCB) and 4-isothiocyanatophenyl 4-butylbenzoate (4TPB) was investigated. Three Miesowicz viscosity coefficients η1, η2, η3 and the refractive indices at different temperatures as well as the enthalpies of the phase transitions were measured. It was stated, that the properties of the induced nematic phase, for example, the nematic phase existing between two smectic regions, are the same as the ones observed in the case of low viscosity nematic mesogens.

To avenge the burnt statues and temples of the Gods : the religious background of the Greek Wars with the "Barbarians"

Abstract In The Clash of Civilizations (1996) Samuel Huntington placed the Persian Wars at the beginning of the long line of clashes between civilizations. To the modern reader the emphasis Huntington puts on the role played by religion in defining Athenian civilization and its conflict with the “barbarians” appears to be consistent with Herodotus’ position on these wars. However, this position overlooks the fact that the ancient polytheistic beliefs and cults implied a particular attitude to religion, unlike that of monotheistic religions. In the ancient Mediterranean world the temples and sacred places were to be universally respected and any violation of this rule was regarded as sacrilege that justified persecution of the wrongdoers, whose ethnicity was of no, or only of secondary, importance. The purpose of this article is to survey the main passages in Herodotus, Thucydides, and Xenophon that treat the wars between the Greeks and Persians and between Greek city-states, and to demonstrate that the line dividing defenders (or avengers) of divine cults from offenders of the gods was not drawn between Greeks and barbarians, but between defenders and offenders.

Dielectric studies of the 4-alkyl-4'-isothio-cyanatobiphenyl (nBT) homologous series (n=4 10)

Preliminary results of the dielectric studies of seven members of the nBT (4-alkyl-4-isothiocyanatobiphenyl, n equals 4 divided by 10) homologous series are presented. The dependence of the static permittivity (epsilon) S, the longitudinal relaxation time (tau) (parallel) and (Delta) H(parallel)) indicate a hardening of this solid-like smectic phase with shortening of the alkyl chain.