Melvin Holmes

Temperature dependence of bulk viscosity in water using acoustic spectroscopy

Despite its fundamental role in the dynamics of compressible fluids, bulk viscosity has received little experimental attention and there remains a paucity of measured data. Acoustic spectroscopy provides a robust and accurate approach to measuring this parameter. Working from the Navier-Stokes model of a compressible fluid one can show that the bulk viscosity makes a significant and measurable contribution to the frequency-squared acoustic attenuation. Here we employ this methodology to determine the bulk viscosity of Millipore water over a temperature range of 7 to 50?C. The measured attenuation spectra are consistent with the theoretical predictions, while the bulk viscosity of water is found to be approximately three times larger than its shear counterpart, reinforcing its significance in acoustic propagation. Moreover, our results demonstrate that this technique can be readily and generally applied to fluids to accurately determine their temperature dependent bulk viscosities.

A LOW FREQUENCY POTENTIAL SCATTERING DESCRIPTION OF ACOUSTIC PROPAGATION IN DISPERSIONS

Ultrasound spectroscopy is a new technique for studying particle size that has great potential due to its ability to size concentrated dispersions such as food emulsions. Successful particle sizing using spectroscopic techniques requires an accurate scattering theory. Single particle scattering theory, first developed by Rayleigh and refined by Epstein and Carhart, is an exact theory for an isolated particle suspended in a medium. The theory involves expansion of the scattered fields as a series of Hankel functions, which, when solved in the far field, give the scattering coefficients. However, the numerical solution for these coefficients is badly conditioned and as a result, it is not possible to guarantee under all circumstances accurate results for calculation of the scattering coefficients. It is also difficult to solve the scattering problem for shapes other than ellipsoids and to account for scattering by more than one particle. Herein is presented a low frequency, asymptotic approximation to singl...

ACOUSTIC PROPAGATION IN DISPERSIONS AND THE GEOMETRIC THEORY OF DIFFRACTION

The ultrasonic characterization of emulsions relies principally upon the theory of thermoacoustic scattering. For a single spherical particle of radius a suspended in a homogeneous medium, the theory provides an exactly soluble solution to the scattering problem. Unfortunately, direct computations with this solution are often ill-conditioned for certain ranges of the acoustic wave number K and thermal wave number L. Recently the authors have developed a low frequency (i.e.,

Inhibitory effect of chlorogenic acid on digestion of potato starch

|Ka|,|La|\ll1

Multiple scattering in dispersions, for long wavelength thermoacoustic solutions

) approach to the theory based on a potential theory technique. This low frequency theory is rapidly convergent and overcomes computation ill-conditioning. In this paper, we pursue the single particle theory and consider the region in which

Enrichment of Biscuits with Matcha Green Tea Powder: Its Impact on Consumer Acceptability and Acute Metabolic Response

|Ka| \ll 1

Temperature Dependence of Bulk Viscosity in Edible Oils using AcousticSpectroscopy

and

Inhibition of pancreatic alpha amylase digestion of potato starch by chlorogenic acid in vitro

|La| \gg 1

Enzyme activity determination using ultrasound

, i.e., the high frequency range of the thermal wavelength. To achieve this, we employ the geometric theory of diffraction. We show that the high frequency solution agrees well with both the experimental measurements and the exact solution in the region wh...

Characterisation of complex fluid media by an angle-scanning ultrasound diffractometer

The effect of the chlorogenic acid isomer 5-O-caffeoylquinic acid (5-CQA) on digestion of potato starch by porcine pancreatic alpha amylase (PPAA) was investigated using isolated starch and cooked potato tuber as substrates. In vitro digestion was performed on five varieties of potato with varying phenolic content. Co- and pre-incubation of PPAA with 5-CQA significantly reduced PPAA activity in a dose dependent manner with an IC50 value of about 2mgmL(-1). Lineweaver-Burk plots indicated that 5-CQA exerts a mixed type inhibition as km increased and Vmax decreased. The total polyphenol content (TPC) of peeled tuber tissue ranged from 320.59 to 528.94mg 100g(-1)dry weight (DW) in raw tubers and 282.03-543.96mg 100g(-1)DW in cooked tubers. With the exception of Désirée, TPC and 5-CQA levels decreased after cooking. Principle component analysis indicated that digestibility is affected by multiple factors including phenolic, dry matter and starch content.