Experimental evidence for excess entropy discontinuities in glass-forming solutions.

Glass transition temperatures T(g) are investigated in aqueous binary and multi-component solutions consisting of citric acid, calcium nitrate (Ca(NO(3))(2)), malonic acid, raffinose, and ammonium bisulfate (NH(4)HSO(4)) using a differential scanning calorimeter. Based on measured glass transition temperatures of binary aqueous mixtures and fitted binary coefficients, the T(g) of multi-component systems can be predicted using mixing rules. However, the experimentally observed T(g) in multi-component solutions show considerable deviations from two theoretical approaches considered.

Ultra-slow water diffusion in aqueous sucrose glasses.

We present measurements of water uptake and release by single micrometre-sized aqueous sucrose particles. The experiments were performed in an electrodynamic balance where the particles can be stored contact-free in a temperature and humidity controlled chamber for several days. Aqueous sucrose particles react to a change in ambient humidity by absorbing/desorbing water from the gas phase.

Parameterizations for ice nucleation in biological and atmospheric systems.

Ice nucleation is an important process in numerous environmental systems such as atmospheric aerosol droplets or biological tissues. Here we analyze two widely used approaches for describing homogeneous ice nucleation in aqueous solutions with respect to their applicability to heterogeneous ice nucleation processes: the lambda approach and the water-activity-based approach. We study experimentally the heterogeneous ice nucleation behaviour of mineral dust particles and biological ice nuclei (Snomax; Pseudomonas syringae) in aqueous solutions as a function of solute concentration for various solutes (sulfuric acid, ammonium sulfate, glucose, and poly(ethylene glycol) with two different molar masses of 400 and 6000 g mol(-1)).