ascertained by performing amplitude sweep experimed on a bohlin gemini rheometer (Malvern Instruments,woecestershire, uk) with a 20 mm diameter parallel plate set at a gap thickness of 50 all experiments were performed over a stress rang of 0.025-50 pa and at a frequency of 1 Hz (intermediate frequency between those those associated with tidal breathing and mucocuiliary clearance) all analyses were performed at 23 to minmise sample dehydration for each sample we report data from the linear regimes established through methods similar to those of vasquez et al