Interaction and Stability of Nanobubbles and Prenucleation Calcium Clusters during Ultrasonic Treatment of Hard Water.

To investigate the stability of nanobubbles in natural hard water, a series of eight samples ranging in hardness from 0 to 332 mg/L CaCO3 were sonicated for periods of 5-45 min with an ultrasonic horn. Conductivity, temperature, ζ-potential, composition, and pH of the water were analyzed, together with the crystal structure of any calcium carbonate precipitate. Quasi-stable populations of bulk nanobubbles in Millipore and soft water are characterized by a ζ-potential of -35 to -20 mV, decaying over 60 h or more. After sonicating the hardest waters for about 10 min, they turn cloudy due to precipitation of amorphous calcium carbonate when the water temperature reaches 40 °C; the ζ-potential then jumps from -10 to +20 mV and remains positive for several days. From an analysis of the change of conductivity of the hard water before and after sonication, it is estimated that 37 ± 5% of calcium was not originally in solution but existed in nanoscale prenucleation clusters, which decorate the nanobubbles formed in the early stages of sonication. Heating and charge screening in the nanobubble colloid cause the decorated bubbles to collapse or disperse, leaving an amorphous precursor of aragonite. Sonicating the soft supernatant increases its conductivity and pH and restores the negative ζ-potential associated with bulk nanobubbles, but there is no further precipitation. Our study of the correlation between nanobubble production and calcium agglomeration spanning the hardness and composition ranges of natural waters shows that the sonication method for introducing nanobubbles is viable only for hard water if it is kept cold; the stability of the nanobubble colloid will be reduced in any case by the presence of dissolved calcium and magnesium.

The role of the speech and language therapist in the rehabilitation of speech, swallowing, voice and trismus in people diagnosed with head and neck cancer.

Head and neck cancer (HNC) and its treatment can have a significant impact on physical and psychosocial wellbeing. A multidisciplinary team (MDT) approach is critical to reduce the potential acute, long-term and late effects of treatment by optimising function at baseline, supporting people during treatment and with rehabilitation post treatment. The key focus for speech and language therapists is to support the holistic needs of people with a focus on speech, swallowing, voice and mouth opening. Effective management is reliant on working with MDT members and interventions are implemented against the background of robust multidimensional baseline evaluation. There have been significant advances in treatment modalities for both primary and recurrent HNC. These include highly conformal radiotherapy modalities, including: image-guided radiotherapy; parotid-sparing and dysphagia-optimised intensity-modulated radiotherapy; and the introduction of intensity-modulated proton therapy, as well as immunotherapy, transoral robotic surgery and surgery with advanced reconstructive techniques. Such treatment advances coupled with a changing patient demographic means that people with HNC are now living longer. However, this is not always without consequences and late treatment effects are a new challenge facing MDTs, requiring high levels of support and rehabilitation.