Water sorption-induced crystallization, structural relaxations and strength analysis of relaxation times in amorphous lactose/whey protein systems

Water sorption-induced crystallization, α-relaxations and relaxation times of freeze-dried lactose/whey protein isolate (WPI) systems were studied using dynamic dewpoint isotherms (DDI) method and dielectric analysis (DEA), respectively. The fractional water sorption behavior of lactose/WPI mixtures shown at aw ≤ 0.44 and the critical aw for water sorption-related crystallization (aw(cr)) of lactose were strongly affected by protein content based on DDI data. DEA results showed that the α-relaxation temperatures of amorphous lactose at various relaxation times were affected by the presence of water and WPI. The α-relaxation-derived strength parameter (S) of amorphous lactose decreased with aw up to 0.44 aw but the presence of WPI increased S. The linear relationship for aw(cr) and S for lactose/WPI mixtures was also established with R2 > 0.98. Therefore, DDI offers another structural investigation of water sorption-related crystallization as governed by aw(cr), and S may be used to describe real time effects of structural relaxations in noncrystalline multicomponent solids.

Characterisation and spectroscopy of laser-cooled atoms with an optical nanofibre

In this thesis, a magneto-optical trap setup is used to laser cool and confine a cloud of 85Rb. The cloud typically contains 108 atoms in a 1 mm3 volume at a temperature in the region of the Doppler Limit (146 _K for 85Rb). To study the cold cloud, a subwavelength optical fibre - a nanofibre, or ONF - is positioned inside the cloud. The ONF can be used in two ways. Firstly, it is an efficient fluorescence collection tool for the cold atoms. Loading times, lifetimes and temperatures can be measured by coupling the atomic fluorescence to the evanescent region of the ONF. Secondly, the ONF is used as a probe beam delivery tool using the evanescent field properties of the device, allowing one to perform spectroscopy on few numbers of near-surface atoms. With improvements in optical density of the cloud, this system is an ideal candidate in which to generate electromagnetically induced transparency and slow light. A theoretical study of the van der Waals and Casimir-Polder interactions between an atom and a dielectric surface is also presented in this work in order to understand their effects in the spectroscopy of near-surface atoms.