Dissipative enhancement of the response of a bistable noisy oscillator to external driving

A study of the linear response susceptibility of a noisy bistable oscillator as a function of damping is carried out using the method of moments. It is found that this dependence, counterintuitively, has a nonmonotonic character and shows a maximum when the driving frequency is comparable to the thermal interwell hopping rate. The possible mechanism responsible for the occurrence of such dissipative sensitivity enhancement is proposed.     

Factors affecting lignin solubility

The solubility of lignin in aqueous NaOH solutions was studied in relation to the lignin molecular weight, temperature, liquid to solid ratio, and ionic strength. A new procedure for determining the content of phenolic hydroxyls in lignin was developed. A formula was suggested for calculating the lignin solubility in aqueous alkali solutions.     

Spectrophotometric investigation of the hetero-association of caffeine and thiazine dye in aqueous solution

The self-association of thiazine dye, Methylene Blue (MB), and its hetero-association with Caffeine (CAF), were studied in aqueous solution by means of spectrophotometry in the visible range of spectrum. Concentration and temperature dependences of molar absorption of the interacting molecules were used to analyse dynamic equilibrium in solution in terms of two-component model of molecular hetero-association. The magnitudes of equilibrium dimerization and hetero-association constants as well as thermodynamic parameters, enthalpy and entropy, were determined. The calculation of the fraction of different types of associates in the mixed solution, containing Methylene Blue and Caffeine, was done. It was concluded that the hetero-association of Methylene Blue and Caffeine molecules results in lower effective concentration of the dye in solution, which may account for the alteration of its biological activity.