372 research outputs found
An interferometric technique for B/A measurement
An isentropic phase method is described for measuringin vitro the acoustic nonlinearity parameterB/A of several aqueous buffers, protein solutions, lipid oils, and emulsions. The technique relies upon the use of an acoustic interferometer to measure the small changes in sound speed that accompany a rapid hydrostaticpressure change of between one and two atmospheres. Average accuracies of 0.85% are attainable with this method
Low-frequency noise reduction of spacecraft structures
Low frequency noise reduction of spacecraft structure
Rheological properties, shape oscillations, and coalescence of liquid drops with surfactants
A method was developed to deduce dynamic interfacial properties of liquid drops. The method involves measuring the frequency and damping of free quadrupole oscillations of an acoustically levitated drop. Experimental results from pure liquid-liquid systems agree well with theoretical predictions. Additionally, the effects of surfactants is considered. Extension of these results to a proposed microgravity experiment on the drop physics module (DPM) in USML-1 are discussed. Efforts are also underway to model the time history of the thickness of the fluid layer between two pre-coalescence drops, and to measure the film thickness experimentally. Preliminary results will be reported, along with plans for coalescence experiments proposed for USML-1
How high the temperature of a liquid be raised without boiling?
How high the temperature of a liquid be raised beyond its boiling point
without vaporizing (known as the limit of superheat) is an interesting subject
of investigation. A new method of finding the limit of superheat of liquids is
presented here. The superheated liquids are taken in the form of drops
suspended in visco elastic gel. The nucleation is detected acoustically by a
sensitive piezo-electric transducer, coupled to a multi channel scaler and the
nucleation is observed as a funtion of time and with increase of temperature.
The limit of superheat measured by the present method supersedes all other
measurements and theoretical predictions in reaching closest to the critical
temperature and warrants improved theoretical predictions.Comment: 10 pages, 1 fig. Phys, Rev. E. (2000) in pres
Superheated Microdrops as Cold Dark Matter Detectors
It is shown that under realistic background considerations, an improvement in
Cold Dark Matter sensitivity of several orders of magnitude is expected from a
detector based on superheated liquid droplets. Such devices are totally
insensitive to minimum ionizing radiation while responsive to nuclear recoils
of energies ~ few keV. They operate on the same principle as the bubble
chamber, but offer unattended, continuous, and safe operation at room
temperature and atmospheric pressure.Comment: 15 pgs, 4 figures include
A Corrected Mixture Law For B/A
A derivation is presented that corrects an expression for the effective acoustic nonlinearity parameter of a mixture of immiscible liquids. The derivation is based upon a mass fraction, rather than volume fraction, formulation
First Dark Matter Limits from a Large-Mass, Low-Background Superheated Droplet Detector
We report on the fabrication aspects and calibration of the first large
active mass ( g) modules of SIMPLE, a search for particle dark matter
using Superheated Droplet Detectors (SDDs). While still limited by the
statistical uncertainty of the small data sample on hand, the first weeks of
operation in the new underground laboratory of Rustrel-Pays d'Apt already
provide a sensitivity to axially-coupled Weakly Interacting Massive Particles
(WIMPs) competitive with leading experiments, confirming SDDs as a convenient,
low-cost alternative for WIMP detection.Comment: Final version, Phys. Rev. Lett. (in press
Surface characterization through shape oscillations of drops in microgravity and 1-g
The goal of these experiments is to determine the rheological properties of liquid drops of single or multiple components in the presence or absence of surface active materials by exciting drops into their quadrupole resonance and observing their free decay. The resulting data coupled with appropriate theory should give a better description of the physics of the underlying phenomena, providing a better foundation than earlier empirical results could. The space environment makes an idealized geometry available (spherical drops) so that theory and experiment can be properly compared, and allows a 'clean' environment, by which is meant an environment in which no solid surfaces come in contact with the drops during the test period. Moreover, by considering the oscillations of intentionally deformed drops in microgravity, a baseline is established for interpreting surface characterization experiments done on the ground by other groups and ours. Experiments performed on the United States Microgravity Laboratory Laboratory (USML-1) demonstrated that shape oscillation experiments could be performed over a wide parameter range, and with a variety of surfactant materials. Results, however, were compromised by an unexpected, slow drop tumbling, some problems with droplet injection, and the presence of bubbles in the drop samples. Nevertheless, initial data suggests that the space environment will be useful in providing baseline data that can serve to validate theory and permit quantitative materials characterization at 1-g
Nonlinear Modes of Liquid Drops as Solitary Waves
The nolinear hydrodynamic equations of the surface of a liquid drop are shown
to be directly connected to Korteweg de Vries (KdV, MKdV) systems, giving
traveling solutions that are cnoidal waves. They generate multiscale patterns
ranging from small harmonic oscillations (linearized model), to nonlinear
oscillations, up through solitary waves. These non-axis-symmetric localized
shapes are also described by a KdV Hamiltonian system. Recently such ``rotons''
were observed experimentally when the shape oscillations of a droplet became
nonlinear. The results apply to drop-like systems from cluster formation to
stellar models, including hyperdeformed nuclei and fission.Comment: 11 pages RevTex, 1 figure p
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