Theory of the incommensurate smectic-A phases in dimesogenic liquid crystals

A mechanism assuming a mismatch between the basic smectic periodicity and the amplitude and phase modulations periods of the mass density wave order parameter is proposed, for describing the incommensurate smectic-A structure found in dimesogenic liquid crystals. The different sequences of phases found in this family of compounds are described theoretically.PACS: 61.30.Cz Molecular and microscopic models and theories of liquid crystal structure - 64.70.Md Transitions in liquid crystals     

Sensitivity of absorptionD-fiber sensors

Using asymptotic expansions, we show that the problem of maximizing the sensitivity of an absorption D-fiber sensor can be solved in a general form if a class of functions describing a profile of the dielectric constant of the fiber is prescribed. The corresponding solutions are found for the truncated parabolic and step profiles. The limits of applicability of the solutions obtained are evaluated. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 390–395, May–June, 2000.