This work reports dynamic video images of the influence of ultrasonic cavitation on the sonocrystallisation of ice at a microscopic level. This has been achieved through the construction of a unique ultrasonic system for an optical microscope. The system consists of (1). an ultrasonic cold stage, (2). a temperature control system, and (3). a microscope and imaging setup. This allows the temperature of a sample to be systematically controlled while it is subjected to simultaneous excitation with alternating pressures in the ultrasonic frequency range. Both the amplitude of excitation and the frequency can be varied. Experiments on ice crystals in pure water and sucrose solutions were conducted. Three distinct phenomena were observed. Firstly, there is a tendency for cavitation bubbles to form at the grain boundaries between ice crystals. Secondly, there is a progressive melting of ice by cavitation bubbles which appear to eat their way into the ice phase. Thirdly, the dendritic ice structures may fragment under the influence of ultrasound, thus increasing the number of nuclei which may subsequently grow (secondary nucleation). These observations form the basis of a significantly enhanced understanding and exploitation of the sonocrystallisation of ice.

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A new thermobalance is described which gives a direct plot of percentage weight loss versus sample temperature, without the need for replotting the results. The unit operates over the range ambient to 1000~ and features a miniature water-cooled furnace in conjunction with an electronic microbalance, giving sensitivities of 1 --250 mg for full scale deflection on a potentiometric recerder. Heating rates of 1--100~ are available and the furnace will cool from 1000~ to 50~C in less than four minutes. Typical applications of the unit are illustrated by reference to a number of inorganic and polymer systems.Although recent years have seen considerable development in the field of differential thermal analysis instrumentation, thermobalance design has not proceeded to such a high level of sophistication. Thus samples of the order of 50-200 mg are still widely used, requiring slow heating rates to obtain good resolution. This, coupled with the slow cooling rate of conventional furnaces, makes thermogravimerry a fairly lengthy process.In addition, the so-called "buoyancy effect" which causes an apparent increase in sample weight [l], requires the results to be replotted before a graph of percentage weight loss versus sample temperature can be obtained.The aim of the present design was to construct a thermobalance which would enable samples of the order of a few mg to be studied with good resolution at high heating rates, with minimum cool-down time between experiments. It was also required that "buoyancy effects" should be reduced to a level where it was possible to obtain a direct reading of the weight changes.

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We report preliminary data from molecular and rheometric characterization to flow characterization of model fluids in benchmark flow problems, in a range of Wi number and Re number flow regimes. The experimental data will be used to critically compare numerical predictions of some well-established constitutive models. We hope to provide physical insight to polymer dynamics in highly non-linear flows, hence to improve constitutive models for a better prediction of dynamics of semi-dilute polymer solutions.