ORCID Profile
0000-0002-9740-2596
Current Organisation
University of Leeds
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Publisher: IOP Publishing
Date: 23-02-2010
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.873365
Publisher: IOP Publishing
Date: 2011
Publisher: SPIE-Intl Soc Optical Eng
Date: 2012
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.MSEC.2013.07.046
Abstract: The aim of this work is to demonstrate that the structural and fluidic properties of polymer foam tissue scaffolds, post-fabrication but prior to the introduction of cells, can be engineered via exposure to high power ultrasound. Our analysis is supported by measurements of fluid uptake during insonification and imaging of the scaffold microstructure via X-ray computed tomography, scanning electron microscopy and acoustic microscopy. The ultrasonic treatment is performed with a frequency of 30 kHz, average intensities up to 80,000 Wm(-2) and exposure times up to 20 h. The treatment is found to increase the mean pore size by over 10%. More striking is the improvement in fluid uptake: for scaffolds with only 40% water uptake via standard immersion techniques, we can routinely achieve full saturation of the scaffold over approximately one hour of exposure. These desirable modifications occur with negligible loss of scaffold integrity and mass, and are optimized when the ultrasound treatment is coupled to a pre-wetting stage with ethanol. Our findings suggest that high power ultrasound is highly targeted towards flow obstructions in the scaffold architecture, thereby providing an efficient means to promote pore interconnectivity and fluid transport in thick foam tissue scaffolds.
Publisher: IOP Publishing
Date: 09-09-2010
DOI: 10.1088/1748-6041/5/5/055004
Abstract: Acoustics offers rich possibilities for characterizing and monitoring the biopolymer structures being employed in the field of biomedical engineering. Here we explore the rudimentary acoustic properties of two common biodegradable polymers: poly(lactic acid) and poly(lactic-co-glycolic acid). A pulse-echo technique is developed to reveal the bulk speed of sound, acoustic impedance and acoustic attenuation of small s les of the polymer across a pertinent temperature range of 0-70 °C. The glass transition appears markedly as both a discontinuity in the first derivative of the speed of sound and a sharp increase in the acoustic attenuation. We further extend our analysis to consider the role of ethanol, whose presence is observed to dramatically modify the acoustic properties and reduce the glass transition temperature of the polymers. Our results highlight the sensitivity of acoustic properties to a range of bulk properties, including visco-elasticity, molecular weight, co-polymer ratio, crystallinity and the presence of plasticizers.
Publisher: Springer Science and Business Media LLC
Date: 05-2007
DOI: 10.1038/NPHYS615
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.873302
Publisher: IOP Publishing
Date: 2011
Publisher: Elsevier
Date: 2013
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 23-11-2017
DOI: 10.1038/S41598-017-16294-5
Abstract: Asphaltenes constitute the heaviest, most polar and aromatic fraction of petroleum crucial to the formation of highly-stable water-in-crude oil emulsions. The latter occur during crude oil production as well as spills and cause difficulties to efficient remediation practice. It is thought that in nanoaggregate form, asphaltenes create elastic layers around water droplets enhancing stability of the emulsion matrix. Ultrasonic characterisation is a high-resolution non-invasive tool in colloidal analysis shown to successfully identify asphaltene nanoaggregation in toluene. The high sensitivity of acoustic velocity to molecular rearrangements and ease in implementation renders it an attractive method to study asphaltene phase properties. Currently, aggregation is thought to correspond to an intersection of two concentration-ultrasonic velocity regressions. Our measurements indicate a variation in the proximity of nanoaggregation which is not accounted for by present models. We attribute this uncertainty to physico-chemical heterogeneity of the asphaltene fraction driven by variation in molecular size and propose a critical nanoaggregation region. We treated asphaltenes from North and South American crude oils with ruthenium ion catalysed oxidation to characterize their n -alkyl appendages attached to aromatic cores. Principal component analysis was performed to investigate the coupling between asphaltene structures and velocity measurements and their impact on aggregation.
Publisher: IOP Publishing
Date: 17-06-2005
Publisher: Elsevier BV
Date: 05-2019
Publisher: IOP Publishing
Date: 10-12-2012
Publisher: Elsevier BV
Date: 2012
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Megan Povey.