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Analysis of pectin biopolymer phase states using acoustic emissions.

ABSTRACT: Acoustic emissions are stress or elastic waves produced by a material under external load. Since acoustic emissions are generated from within and transmitted through the substance, the acoustic signature provides insights into the physical and mechanical properties of the material. In this report, we used a constant velocity probe with force and acoustic emission monitoring to investigate the properties of glass phase and gel phase pectin films. In the gel phase films, a constant velocity uniaxial load produced periodic premonitory acoustic emissions with coincident force variations (saw-tooth pattern). SEM images of the gel phase microarchitecture indicated the presence of slip planes. In contrast, the glass phase films demonstrated early acoustic emissions, but effectively no force or acoustic evidence of periodic or premonitory emissions. Microstructural imaging of the glass phase films indicated the presence of early microcracks as well as dense polymerization of the pectin (without evidence of slip planes). We conclude that the water content in the pectin films contributes to not only the physical properties of the films, but also the stick-slip motion observed with constant uniaxial load. Further, acoustic emissions provide a sensitive and practical measure of this mechanical behavior.

SUBMITTER: Zheng Y

PROVIDER: S-EPMC6936603 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Analysis of pectin biopolymer phase states using acoustic emissions.

Zheng Yifan Y Pierce Aidan A Wagner Willi L WL Scheller Henrik V HV Mohnen Debra D Tsuda Akira A Ackermann Maximilian M Mentzer Steven J SJ

Carbohydrate polymers 20190905

Acoustic emissions are stress or elastic waves produced by a material under external load. Since acoustic emissions are generated from within and transmitted through the substance, the acoustic signature provides insights into the physical and mechanical properties of the material. In this report, we used a constant velocity probe with force and acoustic emission monitoring to investigate the properties of glass phase and gel phase pectin films. In the gel phase films, a constant velocity uniaxi ...[more]

PMID: 31590860

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Project description:BackgroundAcoustic emission (AE) sensing is in use since the late 1960s in drought-induced embolism research as a non-invasive and continuous method. It is very well suited to assess a plant's vulnerability to dehydration. Over the last couple of years, AE sensing has further improved due to progress in AE sensors, data acquisition methods and analysis systems. Despite these recent advances, it is still challenging to detect drought-induced embolism events in the AE sources registered by the sensors during dehydration, which sometimes questions the quantitative potential of AE sensing.ResultsIn quest of a method to separate embolism-related AE signals from other dehydration-related signals, a 2-year-old potted Fraxinus excelsior L. tree was subjected to a drought experiment. Embolism formation was acoustically measured with two broadband point-contact AE sensors while simultaneously being visualized by X-ray computed microtomography (µCT). A machine learning method was used to link visually detected embolism formation by µCT with corresponding AE signals. Specifically, applying linear discriminant analysis (LDA) on the six AE waveform parameters amplitude, counts, duration, signal strength, absolute energy and partial power in the range 100-200 kHz resulted in an embolism-related acoustic vulnerability curve (VCAE-E) better resembling the standard µCT VC (VCCT), both in time and in absolute number of embolized vessels. Interestingly, the unfiltered acoustic vulnerability curve (VCAE) also closely resembled VCCT, indicating that VCs constructed from all registered AE signals did not compromise the quantitative interpretation of the species' vulnerability to drought-induced embolism formation.ConclusionAlthough machine learning could detect similar numbers of embolism-related AE as µCT, there still is insufficient model-based evidence to conclusively attribute these signals to embolism events. Future research should therefore focus on similar experiments with more in-depth analysis of acoustic waveforms, as well as explore the possibility of Fast Fourier transformation (FFT) to remove non-embolism-related AE signals.

Project description:To determine if focused ultrasound disruption of the blood-brain barrier (BBB) can be safely controlled by using real-time modulation of treatment pressures on the basis of acoustic emissions from the exposed microbubbles.All experiments were performed with the approval of the institutional animal care committee. Transcranial focused ultrasound (551.5 kHz, 10-msec bursts, 2-Hz pulse repetition frequency, 2 minute sonication) in conjunction with circulating microbubbles was applied in 86 locations in 27 rats to disrupt the BBB. Acoustic emissions captured during each burst by using a wideband polyvinylidene fluoride hydrophone were analyzed for spectral content and used to adjust treatment pressures. Pressures were increased incrementally after each burst until ultraharmonic emissions were detected, at which point the pressure was reduced to a percentage of the pressure required to induce the ultraharmonics and was maintained for the remainder of the sonication. Disruption was evaluated at contrast material-enhanced T1-weighted magnetic resonance (MR) imaging. Mean enhancement was calculated by averaging the signal intensity at the focus over a 3 × 3-pixel region of interest and comparing it with that in nonsonicated tissue. Histologic analysis was performed to determine the extent of damage to the tissue. Statistical analysis was performed by using Student t tests.For sonications resulting in BBB disruption, the mean peak pressure was 0.28 MPa ± 0.05 (standard deviation) (range, 0.18-0.40 MPa). By using the control algorithm, a linear relationship was found between the scaling level and the mean enhancement on T1-weighted MR images after contrast agent injection. At a 50% scaling level, mean enhancement of 19.6% ± 1.7 (standard error of the mean) was achieved without inducing damage. At higher scaling levels, histologic analysis revealed gross tissue damage, while at a 50% scaling level, no damage was observed at high-field-strength MR imaging or histologic examination 8 days after treatment.This study demonstrates that acoustic emissions can be used to actively control focused ultrasound exposures for the safe induction of BBB disruption.

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Analysis of pectin biopolymer phase states using acoustic emissions.

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Analysis of pectin biopolymer phase states using acoustic emissions.

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