arXiv subjects

Robin O. Cleveland

Publications and source records attributed to Robin O. Cleveland.

4 recordsLinked to original sources

arXiv2019

Photo and acoustic emissions from the non-equilibrium phase transition at the interface during cavitation

This study investigates the emission of light and sound from cavitation caused by intense pressure pulses in water. Based on time-resolved measurements of (a) pressure waveform at the focus, (b) light scattering upon cavitation, (c) acoustic emission, and (d) photoemission (sonoluminescence) it is shown that emissions occur upon the creation or expansion as well as the collapse of the cavity. These results suggest that the thermodynamic irreversibility, resulting from non-equilibrium phase transition and changes in surface entropy, is a basis for photo and acoustic emissions during cavitation.

physics.flu-dyn↗

arXiv2019

Thermodynamic State of the Interface during Acoustic Cavitation in Lipid Suspensions

The thermodynamic state of lipid interfaces was observed during shock wave induced cavitation in water with sub-microsecond resolution, using the emission spectra of hydration-sensitive fluorescent probes co-localized at the interface. The experiments show that the cavitation threshold is lowest near a phase transition of the lipid interface. The cavitation collapse time and the maximum state change during cavitation are found to be a function of both the driving pressure and the initial state of the lipid interface. The experiments show dehydration and crystallization of lipids during the expansion phase of cavitation, suggesting that the heat of vaporization is absorbed from within the interface, which is adiabatically uncoupled from the free water. The study underlines the critical role of the thermodynamic state of the interface in cavitation dynamics, which has mechanistic implications for ultrasound-mediated drug delivery, acoustic nerve stimulation, ultrasound contrast agents, and the nucleation of ice during cavitation.

cond-mat.soft↗

arXiv2018

On measuring the acoustic state changes in lipid membranes using fluorescent probes

Ultrasound is increasingly being used to modulate the properties of biological membranes for applications in drug delivery and neuromodulation. While various studies have investigated the mechanical aspect of the interaction such as acoustic absorption and membrane deformation, it is not clear how these effects transduce into biological functions, for example, changes in the permeability or the enzymatic activity of the membrane. A critical aspect of the activity of an enzyme is the thermal fluctuations of its solvation or hydration shell. Thermal fluctuations are also known to be directly related to membrane permeability. Here solvation shell changes of lipid membranes subject to an acoustic impulse were investigated using a fluorescence probe, Laurdan. Laurdan was embedded in multi-lamellar lipid vesicles in water, which were exposed to broadband pressure impulses of the order of 1MPa peak amplitude and 10μs pulse duration. An instrument was developed to monitor changes in the emission spectrum of the dye at two wavelengths with sub-microsecond temporal resolution. The experiments show that changes in the emission spectrum, and hence the fluctuations of the solvation shell, are related to the changes in the thermodynamic state of the membrane and correlated with the compression and rarefaction of the incident sound wave. The results suggest that acoustic fields affect the state of a lipid membrane and therefore can potentially modulate the kinetics of channels and proteins embedded in the membrane.

cond-mat.soft↗

arXiv2011

Multi-parameter acoustic imaging of uniform objects in inhomogeneous media

The problem studied in this paper is ultrasound image reconstruction from frequency-domain measurements of the scattered field from an object with contrast in attenuation and sound speed. The case where the object has uniform but unknown contrast in these properties relative to the background is considered. Background clutter is taken into account in a physically realistic manner by considering an exact scattering model for randomly located small scatterers that vary in sound speed. The resulting statistical characteristics of the interference is incorporated into the imaging solution, which includes applying a total-variation minimization based approach where the relative effect of perturbation in sound speed to attenuation is included as a parameter. Convex optimization methods provide the basis for the reconstruction algorithm. Numerical data for inversion examples are generated by solving the discretized Lippman-Schwinger equation for the object and speckle-forming scatterers in the background. A statistical model based on the Born approximation is used for reconstruction of the object profile. Results are presented for a two dimensional problem in terms of classification performance and compared to minimum-l2-norm reconstruction. Classification using the proposed method is shown to be robust down to a signal-to-clutter ratio of less than 1 dB.

cs.CV↗