Pitch in esophageal speech.
Most reports on pitch in esophageal speech emphasize that it is low-pitched with a measured fundamental frequency rarely higher than 100 cps. Our investigations show, however, that much esophageal 'phonation' lacks periodicity and, therefore, a fundamental frequency (i.e. pitch in the accepted sense). An auditory impression of pitch modulation can, nevertheless, be created by physical properties other than a varying harmonic structure. Our sample includes a rare case of truly high-pitched esophageal phonation with a fundamental frequency in the upper limit of the voice an octave higher than the highest reported in the literature. High-pitched phonation apparently requires a vibratory source in a 'mode' different from that of low-pitched phonation and should therefore be distinguished from it in discussing pitch in esophageal voice.
A note on pitch control in esophageal speech.
An unusual case of  esophageal pitch control first  discussed in this Journal is re-examined in the light of  additional data. It is claimed that high-pitched stressed vowels show evidence of  diplophonia, a possibility not described in earlier studies of  this case.
Experimental energy barriers to anions transporting through nanofiltration membranes.
Environmentally relevant contaminants fluoride, chloride, nitrate, and nitrite face Arrhenius energy barriers during transport through nanofiltration (NF) membranes. The energy barriers were quantified using crossflow filtration experiments and were in the range of 7-17 kcal·mol(-1), according to ion type and membrane type (Filmtec NF90 and NF270). Fluoride faced a comparatively high energy barrier for both membranes. This can be explained by the strong hydration energy of fluoride rather than other ion properties such as bare ion radius, fully hydrated radius, Stokes radius, diffusion coefficient, or ion charge. The energy barrier for fluoride decreased with pressure, indicating an impact of directional force on energy barriers. The influence of temperature-induced pore radius variability and viscosity on energy barriers was considered. The novel link between energy barriers and ion properties emphasizes the importance of ion hydration and/or partial dehydration mechanisms in determining transport in NF.