20150414 Jason Raymond gives colloquium talk in the Physics department.

Jason Raymond, who was a member of the Ultrasonics group from 2002-2009, returned to give a colloquium talk on his work on echogenic liposomes.  Jason is currently finishing up a stint at the University of Cincinnati where he got his PhD in Biomedical Engineering.

Abstract

Lipid-shelled Ultrasound Contrast Agents for Imaging and Therapy: Stable and Unstable Dynamics

Lipid-shelled ultrasound contrast agents known as “echogenic liposomes” are nanoparticle theragnostic agents being developed to target and treat cardiovascular disease. This talk will present recent results using an ultra-high-speed optical imaging approach to investigate the acoustic response of these agents. The investigations utilize an ultra high-speed imaging system (“Brandaris 128”, Rotterdam, the Netherlands) which was developed for imaging physical phenomena such as ultrasound-microbubble interaction at up to 20 million frames per second. Results of two studies using this unique imaging facility will be presented. In the first study, we demonstrate a method to estimate the acousto-mechanical properties based on the impulse response. In the second study, we investigate the response to multiple-cycle acoustic pulses, which result in loss of gas from individual particles. These studies demonstrate that acoustically-active or “echogenic” liposomes can be considered a theragnostic agent, with both stable and unstable dynamics that can be exploited using different ultrasound parameter regimes.

20150407: Upcoming April 2015, Taylor Miller, Davis Rogers and Conner Tierney to defend Honors Theses.

Taylor Miller, Davis Rogers and Conner Tierney will defend their honors theses this April 2015.  Taylor's research concerns the study of ultrasound transducer fields using the angular spectrum method, Davis studied standing waves produced in ultrasound transducer fields while Connor studied the mechanics of shear waves in a micellar fluid. All three students are physics majors andhave worked with the Physical Ultrasonics group for more than one year.

20150326: Upcoming 04/14/2015, Jason Raymond will give a colloquium talk

Jason Raymond, a past member of the Physical Ultrasonics group, will return to the University of Mississippi to give a talk in the Physics Department colloquium on April 14.  Jason is currently at the University of Cincinnati in the Biomedical Engineering program.  The colloquium will bea 50 minute talk at the graduate student level with 10 minutes for questions.

20150219: Research talks at the 79th MAS meeting.

Ukesh Koju, Taylor Miller and Nazanin Omidi gave talks at the the 79th Mississippi Academy of Sciences Meeting in Hattiesburg.

ULTRASONIC BAND GAPS IN TWO-DIMENSIONAL PHONONIC METAMATERIALS WITH PERIODIC ARRAYS OF COPPER RODS.  Ukesh Koju and Joel Mobley.  Phononic crystals are composite metamaterials consisting of periodic arrays of scatterers embedded in a homogenous matrix. Under certain conditions these crystals exhibit forbidden gaps in their ultrasonic transmission spectra (i.e., band gaps) irrespective of the direction of propagation of elastic waves. The contrast between the physical characteristics (e.g., density and elastic moduli) of the scatterers and of the matrix mainly determines the width of the band gaps. Other characteristics such as filling factor, geometry of the array, and the shape of the scatterers also contribute to gap widths. We present some examples of band gaps in the elastic wave spectrum of two-dimensional phononic crystals composed of periodically arranged copper rods in various matrices.

AN ASSESSMENT OF THE ANGULAR SPECTRUM METHOD FOR THE PROPAGATION OF ULTRASONIC FIELDS. Taylor Miller and Joel Mobley.  The goal of this work is to test the validity of the angular spectrum technique as applied to broadband pressure fields generated in water by a submerged ultrasonic source. Using a motorized scanning system, detailed hydrophone measurements of the pressure field emitted by an ultrasonic immersion transducer (d=12.7 mm) were acquired over transverse planes at 10 axial depths. Using Fourier analysis, the measured time-domain fields are transformed into frequency-resolved field distributions. The angular spectrum technique is then applied to simulate the propagation of the fields among the 10 data planes. Through this work we will be able to assess the capabilities and limitations of the angular spectrum technique as applied to low-MHz ultrasonic waves in water.

COMPUTING OF ULTRASONIC PRESSURE FIELDS IN FELINE BRAIN. Nazanin Omidi, Charles Church, and Cecille Labuda.  The overall goal of this project is to determine the actual acoustic pressure present during experiments performed in the brains of anesthetized cats. The project involved calculation of the acoustic pressure waveform in cat brain produced by a spherically focused transducer given the source pressure amplitude,frequency,transducer diameter and focal length. For low source pressure,the focal intensity is matched to experimentally determined values,and the computed wave forms are the same as those determined using linear theory. For higher source pressures,the intensities may still match,but the pressure waveform must be computed using nonlinear theory.

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