3D Printing and processing of miniaturized transducers with near-pristine piezoelectric ceramics for localized cavitation.

The performance of ultrasonic transducers is largely determined by the piezoelectric properties and geometries of their active elements. Due to the brittle nature of piezoceramics, existing processing tools for piezoelectric elements only achieve simple geometries, including flat disks, cylinders, cubes and rings. While advances in additive manufacturing give rise to free-form fabrication of piezoceramics, the resultant transducers suffer from high porosity, weak piezoelectric responses, and limited geometrical flexibility.

Thermal Convection in a Central Force Field Mediated by Sound.

Convection in radial force fields is a fundamental process behind weather on Earth and the Sun, as well as magnetic dynamo action in both. Until now, benchtop experiments have been unable to study convection in radial force fields due to the inability to generate radial forces of sufficient strength. Recently, it has been appreciated that sound, when averaged over many cycles, exerts a force on density gradients in the gas it travels through.

Prediction of Short Time Qubit Readout via Measurement of the Next Quantum Jump of a Coupled Damped Driven Harmonic Oscillator.

The dynamics of the next quantum jump for a qubit [two level system] coupled to a readout resonator [damped driven harmonic oscillator] is calculated. A quantum mechanical treatment of readout resonator reveals nonexponential short time behavior which could facilitate detection of the state of the qubit faster than the resonator lifetime.

Tumescent Injections in Subcutaneous Pig Tissue Disperse Fluids Volumetrically and Maintain Elevated Local Concentrations of Additives for Several Hours, Suggesting a Treatment for Drug Resistant Wounds.

Purpose: Bolus injection of fluid into subcutaneous tissue results in accumulation of fluid at the injection site. The fluid does not form a pool. Rather, the injection pressure forces the interstitial matrix to expand to accommodate the excess fluid in its volume, and the fluid becomes bound similar to that in a hydrogel.

Dynamics of strongly coupled two-component plasma via ultrafast spectroscopy.

A combination of ultrafast emission and transmission spectroscopy is presented that provides a model-independent temperature measurement and tracking of the expansion dynamics for a dense, strongly coupled plasma. For femtosecond laser breakdown of hydrogen gas at 10 bar, we observe a 30,000 K two-component plasma for hundreds of picoseconds where both electrons and protons have a strong coupling parameter value of $\Gamma \sim{0.5}$Γ∼0.

Acoustic self-oscillation in a spherical microwave plasma.

We present a method of sound amplification and self-oscillation in high pressure partially ionized gas. Continuous microwaves incident on partially ionized gas may sustain and amplify an acoustic field if increased ionization during the sound field's adiabatic compression enhances rf power absorption. Amplifying sound in this way enables the generation of high amplitude sound in a cavity containing partially ionized gas without mechanical driving or precise knowledge of its resonance frequency.

Sparks as sub-nanosecond, broadband light switches.

We evaluate spark micro-discharges as the working element of laser switches that can operate on sub-nanosecond timescales, function over a broad range of wavelengths, and handle high laser power. Sparks were generated in room temperature argon at 11-51 bar and xenon at 3-11.6 bar.

Acoustic resonances in gas-filled spherical bulb with parabolic temperature profile.

Acoustics is used to probe the temperature profile within a sulfur plasma lamp. A spherically symmetric temperature profile is assumed that drops with the square of the radius, consistent with a constant volumetric heating model. Acoustic resonance frequencies are calculated exactly in the case of an ideal gas.

Subcutaneous cefazolin to reduce surgical site infections in a porcine model.

Background: Surgical site infections (SSIs) pose a significant health and financial burden. A key aspect of appropriate prophylaxis is the administration of antibiotics intravenously (IV). However, subcutaneous administration of antibiotics is not well described in the literature.

Simultaneous measurement of triboelectrification and triboluminescence of crystalline materials.

Triboelectrification has been studied for over 2500 years, yet there is still a lack of fundamental understanding as to its origin. Given its utility in areas such as xerography, powder spray painting, and energy harvesting, many devices have been made to investigate triboelectrification at many length-scales, though few seek to additionally make use of triboluminescence: the emission of electromagnetic radiation immediately following a charge separation event. As devices for measuring triboelectrification became smaller and smaller, now measuring down to the atomic scale with atomic force microscope based designs, an appreciation for the collective and multi-scale nature of triboelectrification has perhaps abated.

Interstitial Matrix Prevents Therapeutic Ultrasound From Causing Inertial Cavitation in Tumescent Subcutaneous Tissue.

We search for cavitation in tumescent subcutaneous tissue of a live pig under application of pulsed, 1-MHz ultrasound at 8 W cm spatial peak and pulse-averaged intensity. We find no evidence of broadband acoustic emission indicative of inertial cavitation. These acoustic parameters are representative of those used in external-ultrasound-assisted lipoplasty and in physical therapy and our null result brings into question the role of cavitation in those applications.

Cleaving the Halqeh-ye-nur diamonds: a dynamic fracture analysis.

The degree of surface roughness and clarity with which a surface in a brittle material can be formed via fracture is known to be related to the speed of the propagating crack. Cracks traversing a brittle material at low speed produce very smooth surfaces, while those propagating faster create less reflective and rough surfaces (Buehler MJ, Gao H. 2006 Nature 439, 307-310 (doi:10.

Opacity and transport measurements reveal that dilute plasma models of sonoluminescence are not valid.

A strong interaction between a nanosecond laser and a 70 μm radius sonoluminescing plasma is achieved. The overall response of the system results in a factor of 2 increase in temperature as determined by its spectrum. Images of the interaction reveal that light energy is absorbed and trapped in a region smaller than the sonoluminescence emitting region of the bubble for over 100 ns.

Phase transition to an opaque plasma in a sonoluminescing bubble.

Time-resolved spectrum measurements of a sonoluminescing Xe bubble reveal a transition from transparency to an opaque Planck blackbody. As the temperature is <10 000  K and the density is below liquid density, the photon scattering length is 10 000 times too large to explain its opacity. We resolve this issue with a model that reduces the ionization potential.

100-Watt sonoluminescence generated by 2.5-atmosphere-pressure pulses.

A Xenon gas bubble introduced into a vertically suspended steel cylinder is driven to sonoluminescence by impacting the apparatus against a solid steel base. This produces a 150-ns flash of broadband light that exceeds 100-W peak intensity and has a spectral temperature of 10,200 K. This bubble system, which yields light with a single shot, emits very powerful sonoluminescence.

Molecular dynamics of extreme mass segregation in a rapidly collapsing bubble.

A molecular dynamic simulation of a mixture of light and heavy gases in a rapidly imploding sphere exhibits virtually complete segregation. The lighter gas collects at the focus of the sphere and reaches a temperature that is several orders of magnitude higher than when its concentration is 100%. Implosion parameters are chosen via a theoretical fit to an observed sonoluminescing bubble with an extreme expansion ratio (25:1) of maximum to ambient radii.

Convective corrections to the linear diffusion equation.

The classical problem of the diffusion of heat in a homogeneous medium is reexamined, the medium being confined by fixed boundaries maintained at a fixed temperature. When the thermal diffusivity is small, the relaxation of the temperature of the medium to that of the boundary proceeds on two time scales, one associated with a lightly damped high-frequency acoustic mode and the other with an aperiodically damped diffusive mode. Considering for simplicity a spherical configuration, it is shown that the latter does not obey the classical linear heat conduction equation.

Measurement of pressure and density inside a single sonoluminescing bubble.

The average pressure inside a sonoluminescing bubble in sulfuric acid has been determined by two independent techniques: (1) plasma diagnostics applied to Ar atom emission lines, and (2) light scattering measurements of bubble radius vs time. For dimly luminescing bubbles, both methods yield intracavity pressures approximately 1500 bar. Upon stronger acoustic driving of the bubble, the sonoluminescence intensity increases 10,000-fold, spectral lines are no longer resolved, and radius vs time measurements yield internal pressures > 3700 bar.

Dynamics of a sonoluminescing bubble in sulfuric acid.

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (approximately 10 ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Sonoluminescence from a single bubble driven at 1 megahertz.

Measurements of the spectrum of sonoluminescence from an isolated bubble driven at 1 MHz are well fit by assuming thermal bremsstrahlung from a transparent 10(6) degree plasma. According to this interpretation, the photon-matter mean free path is larger than the light-emitting radius of a 1 MHz bubble, but smaller than the light-emitting radius for bubbles driven at approximately 40 kHz, thus accounting for the observed blackbody spectrum at 40 kHz.

Molecular dynamics simulation of the response of a gas to a spherical piston: implications for sonoluminescence.

Sonoluminescence is the phenomena of light emission from a collapsing gas bubble in a liquid. Theoretical explanations of this extreme energy focusing are controversial and difficult to validate experimentally. We propose to use molecular dynamics simulations of the collapsing gas bubble to clarify the energy focusing mechanism, and determine physical parameters that restrict theories of the light emitting mechanism.