Effect of molecular oxygen on concentration autooscillations and autowaves in the Belousov-Zhabotinskii reaction

Modulation of the shape and speed of a chemical wave in an unstirred Belousov-Zhabotinsky reaction by a rotating magnet

The objective of this study was to observe whether a rotating magnetic field (RMF) could change the anomalous chemical wave propagation induced by a moderate-intensity gradient static magnetic field (SMF) in an unstirred Belousov-Zhabotinsky (BZ) reaction. The application of the SMF (maximum magnetic flux density = 0.22 T, maximum magnetic flux density gradient = 25.5 T/m, and peak magnetic force product (flux density × gradient) = 4 T(2) /m) accelerated the propagation velocity in a two-dimensional pattern. Characteristic anomalous patterns of the wavefront shape were generated and the patterns were dependent on the SMF distribution. The deformation and increase in the propagation velocity were diminished by the application of an RMF at a rotation rate of 1 rpm for a few minutes. Numerical simulation by means of the time-averaged value of the magnetic flux density gradient or the MF gradient force over one rotation partially supported the experimental observations. These considerations suggest that RMF exposure modulates the chemical wave propagation and that the degree of modulation could be, at least in part, dependent on the time-averaged MF distribution over one rotation. Bioelectromagnetics 34:220-230, 2013. © 2012 Wiley Periodicals, Inc.

Synthesis, Structure, and Acidic Properties of MCM-41 Functionalized with Phosphate and Titanium Phosphate Groups

Mesoporous molecular sieves Si-MCM-41 (purely siliceous) and Ti-MCM-41 (partly covered with a surface layer of TiO2) were functionalized with phosphate groups by treatment with POCl3 (denoted -MCM-41(P)and Ti-MCM-41(P), respectively). With the use of TEM, X-ray diffraction, and N2 adsorption, it was shown that the initial hexagonal structure, the high specific surface area, and porosity are retained in the functionalized materials but are not as good as in the starting materials. 1H MAS NMR and 31P MAS NMR revealed that the surface of Si-MCM-41(P) consists of silicon phosphate and pyrophosphate species. That of Ti-MCM-41(P) additionally contains titanium dihydro-, hydro-, and pyrophosphate species, the latter being predominant. TPD of adsorbed ammonia for Si-MCM-41(P) and Ti-MCM-41(P) showed that functionalization leads to the creation of moderate and strong acid sites. A combination of mesoporous structure with acidic properties makes the MCM-41 functionalized with phosphate groups promising for use as solid acid catalysts.