A Raman Study of Morphotropic Phase Boundary in PbZr1-xTixO3 at low temperatures

Raman spectra of PbZr1-xTixO3 ceramics with titanium concentration varying between 0.40 and 0.60 were measured at 7 K. By observing the concentration-frequency dependence of vibrational modes, we identified the boundaries among rhombohedral, monoclinic, and tetragonal ferroelectric phases. The analysis of the spectra was made in the view of theory group analysis making possible the assignment of some modes for the monoclinic phase.Comment: 5 pages, 4 figure

Analytical aspects of enzyme reversible inhibition

simple graphical method for the determination of reversible inhibition type,inhibitio constant(Ki) and estimation of fifty per cent of inhibition I50 of an enzyme reaction is described.The method consists of plotting experimental data as “degree ofinhibition” versus the inhibitor concentration at two or more concentrations of substrate.Diagnosis of inhibition type is based on determination of I50 and the observation of the shift of the inhibition curves.Relationship between I50 and inhibition constant Ki was discussed. As implified hyperbolae equation of degree of inhibition showing kinetic orders of 1 and zero at low and high concentrations of inhibitors respectively is proposed.The relative error of inhibitor concentration increased drastically when degree of inhibition reached values of 90%.Examples of published inhibition reports as well as an experimental example of amperometric biosensor based on tyrosinase inhibition by benzoic acid were in agreemen with the proposed theoretical approach