20141028 Article published in EPJH: On the mathematics underlying dispersion relations.

Cecille Labuda and Iwo Labuda. On the mathematics underlying dispersion relations. EPJH. http://dx.doi.org/10.1140/epjh/e2014-50021-1

Abstract. The history of mathematical methods underlying the study of dispersion relations in physics is discussed. In particular, some misconceptions connected with a theorem known in the physics literature as Titchmarsh’s Theorem are addressed. It is pointed out that the aforementioned theorem is a compilation of two well-known theorems in mathematics, the Paley-Wiener theorem and the Marcel Riesz theorem.

20140605 Talk at ASA Spring Meeting: Shear wave propagation in worm-like micellar fluids

Josh R. Gladden, Rachel Crim, Amanda Gamble and Cecille Labuda. Shear wave propagation in worm-like micellar fluids. J. Acoust. Soc. Am. 135, 2218 (2014).

Abstract. In viscous Newtonian fluids, support of shear waves are limited to the viscous boundary layer. Non-Newtonian fluids which have shear modulus, however, support shear waves over much longer distances. The restoring force responsible for the shear wave propagation arises from the entanglement of high aspect ratio macromolecules. We report low frequency (30–60 Hz) shear wave studies of aqueous worm-like micellar fluids composed of cetyltrimethylammonium bromide (CTAB) for the surfactant and sodium salicylate (NaSAL) as the salt over a wide concentration range (20–500 mM CTAB). Shear speeds range from 75 to 700 mm/s over this concentration range at room temperature with evidence of two phase transitions at 200 mM and 375 mM CTAB. Shear stress attenuation and temperature resolved measurements between 20 and 40 C will also be presented.

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