Energy dispersive X-ray fluorescence analysis of airborne particulate matter

Positron annihilation lifetime technique was applied to study the electric field dependence of size, intensity and size distribution of free volumes in various liquid crystals negative nematic MBBA(N-(4-methoxybenzylidene)-4-n-butylaniline), positive nematic 5CB (4-cyano-4-n-pentylbiphenyl) and cholesteric mixture of MBBA and cholesteryl oleate. Positron annihilation decay curves were obtained in the direct and alternate electric field range from 0 to 120 V/mm, and annihilation curves were resolved into four lifetime components. The relation between the free volume parameters and the variation of molecular alignment is discussed for nematic and cholesteric liquid crystals.