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Dysphagia is a common, debilitating and potentially life-threatening sequela of concurrent chemoradiation for head and neck malignancy. Physicians should be aware that the clinical manifestations of aspiration may be unreliable and insidious, because of the depressed cough reflex. Modified and traditional barium swallows should be performed following treatment to assess the safety of oral feeding and the structural integrity of the pharynx and esophagus. Patients with severe dysphagia may benefit from rehabilitation. Tube feeding should be continued for those with aspiration.

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The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA.