Processes associated with ionic current rectification at a 2D-titanate nanosheet deposit on a microhole poly(ethylene terephthalate) substrate

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca²⁺ and Mg²⁺ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu₄⁺ is shown to ‘invert’ the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed.

     

s] and [sh] as a function of linguapalatal contact place and sibilant groove width

Sibilant groove place and width were initially examined during [s] [s] in isolation and in CV and VC syllables. The [s] was found to be produced through a 6- to 8-mm-wide groove near the front of the alveolar ridge by one talker and near the back of the ridge by the other. [s] was produced through a 10- to 12-mm groove behind the posterior border of the alveolar ridge by both. In the second experiment three subjects used visual articulatory feedback to vary sibilant groove width and place systematically. One subject was able to do this with comparatively few retrials; one had difficulty with certain targeted grooves; one had difficulty with many targeted grooves. The noises generated were replayed to 14 listeners who labeled them as "s," "probably s," "probably sh," or "sh." They usually heard the sound as [s] when the grooves were narrow and near the front of the alveolar process, [s] when the groove was wider and behind the alveolar process. Noise through grooves that matched natural speech places and widths usually produced higher listener recognition scores. Exceptions were found when the subjects had unusual difficulty in achieving stipulated groove widths and places.     

A new model for Boolean algebra

This new model for set theory is a graph. It is similar in many ways to a Venn diagram or Karnaugh map, but it does not pose as a rival, merely as an alternative model which may be useful in some contexts. Defined with reference to the duality of lines and points, the graph is a fitting framework in which to display the rich duality of Boolean algebra.

In the first four sections the graph is developed as a natural embodiment of Boolean theory and it is hoped that it will be seen, not as a more computational device but as helpful for demonstrating Boolean theory. The second half of the article is devoted to practical applications. The graph can be applied (and has been applied in school teaching) extensively in set theory, in logic, in probability, in genetics and in switching circuits, but space does not allow the elaboration of all these in detail. So this article concentrates mainly on one of these applications, switching circuits. The graph is used to simplify and minimize logic circuits with techniques different from Karnaugh's and in some instances more comprehensive.