Nonlinear dynamics of gas bubbles in viscoelastic media

This is the published version. Copyright © 2005 Acoustical Society of AmericaUnderstanding the behavior of cavitation bubbles driven by ultrasonic fields is an important problem in biomedical acoustics. The Keller–Miksis equation for nonlinear bubble dynamics is combined with the Voigt model for viscoelastic media. Using experimentally determined values, the effects of elasticity on bubble oscillations are studied. Inertial cavitation thresholds are determined using Rmax/R0=2, and subharmonic emissions are also estimated. The elasticity increases the threshold pressure for inertial cavitation, and subharmonic signals are significant only in a certain region of radii and driving pressures at a given frequency. These results should prove useful in cavitationdetection and bubble-enhanced imaging work

A model for the dynamics of gas bubbles in soft tissue

This is the published version. Copyright 2005 Acoustical Society of AmericaUnderstanding the behavior of cavitation bubbles driven by ultrasonic fields is an important problem in biomedical acoustics. Keller-Miksis equation, which can account for the large amplitude oscillations of bubbles, is rederived in this paper and combined with a viscoelasticmodel to account for the strain-stress relation. The viscoelasticmodel used in this study is the Voigt model. It is shown that only the viscous damping term in the original equation needs to be modified to account for the effect of elasticity. With experiment determined viscoelasticproperties, the effects of elasticity on bubble oscillations are studied. Specifically, the inertial cavitation thresholds are determined using Rmax∕R0, and subharmonic signals from the emission of an oscillating bubble are estimated. The results show that the presence of the elasticity increases the threshold pressure for a bubble to oscillate inertially, and subharmonic signals may only be detectable in certain ranges of radius and pressure amplitude. These results should be easy to verify experimentally, and they may also be useful in cavitation detection and bubble-enhanced imaging

Ultrasound Biosafety Considerations for the Practicing Sonographer and Sonologist

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135175/1/jum2009282139.pd

Yeast Isw1p forms two separable complexes in vivo - Supplementary Materials Only

There are several classes of ATP-dependent chromatin remodeling complexes, which modulate the structure of chromatin to regulate a variety of cellular processes. The budding yeast, Saccharomyces cerevisiae, encodes two ATPases of the ISWI class, Isw1p and Isw2p. Previously Isw1p was shown to copurify with three other proteins. Here we identify these associated proteins and show that Isw1p forms two separable complexes in vivo (designated Isw1a and Isw1b). Biochemical assays revealed that while both have equivalent nucleosome-stimulated ATPase activities, Isw1a and Isw1b differ in their abilities to bind to DNA and nucleosomal substrates, which possibly accounts for differences in specific activities in nucleosomal spacing and sliding. In vivo, the two Isw1 complexes have overlapping functions in transcriptional regulation of some genes yet distinct functions at others. In addition, these complexes show different contributions to cell growth at elevated temperatures

Electric field induced spectra of molecular hydrogen, deuterium and deuterium hydride

The electric field induced spectra of molecular hydrogen, deuterium and deuterium hydride was observed in the pressure range of 0 to 600 psi. Thirteen lines each of the fundamental vibration-rotation band were observed for hydrogen and deuterium and nine were observed for deuterium hydride. A plot of line position versus density yielded zero pressure line positions. Molecular constants were derived from the zero pressure values.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33231/1/0000621.pd

The Risk of Exposure to Diagnostic Ultrasound in Postnatal Subjects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135382/1/jum2008274565.pd

On the multi-periodicities in the X-ray dipper XB 1916-053

Using the Rossi X-ray Timing Explorer and the Nordic Optical Telescope we have obtained the highest ever quality X-ray/white-light high-speed photometry of XB 1916-053. We refine the X-ray period (P_X) to 3000.6+/-0.2s via a restricted cycle counting approach. Using our complete optical lightcurve, we have extended the optical period (P_opt) ephemeris by another 4 years, providing further evidence for its stability, although a slightly longer period of 3027.555+/-0.002s now provides a marginally better fit. Moreover, modulations at both P_X and P_opt are present in the optical data, with the former dominating the nightly lightcurves (i.e. a few cycles of data). We have also attempted to determine the ``beat'' period, as seen in the repeating evolution of the X-ray dip structure, and the variation in primary dip phase. We find that a quasi-period of 4.74+/-0.05d provides the best fit to the data, even then requiring phase shifts between cycles, with the expected 3.90d ``beat'' of P_X and P_opt appearing to be less likely. Finally, considering the nature of each of these temporal phenomena, we outline possible models, which could explain all of the observed behaviour of this enigmatic source, focusing on which of P_X or P_opt is the binary period.Comment: 22 pages, 17 figures (none require colour printing), accepted for publication in MNRA

Cardiorespiratory fitness, adiposity and incident asthma in adults

Available large-scale prospective studies on adiposity and asthma used body mass index as an indicator of adiposity. Studies involving more accurate measures of adiposity, such as body fat percentage (BF%), are needed to confirm or contrast body mass index - related results. Cardiorepiratory fitness is a strong predictor of morbidity and mortality, and the available literature suggests that moderate-high cardiorespiratory fitness reduces many of the health hazards associated with obesity. The present study aimed: 1) to examine whether cardiorespiratory fitness and/or BF% are associated with subsequent acquisition of asthma in adults; and 2) to test the hypothesis that a high cardiorespiratory fitness level can reduce the risk of incident asthma in individuals with excess adiposity

Coastal Ocean Processes : a science prospectus

CoOP (Coastal Ocean Processes) is an organization meant to study major interdisciplinary scientific problems in the coastal ocean. Its goal is "to obtain a new level of quantitative understanding of the processes that dominate the transformations, transport and fates of biologically, chemically and geologically important matter on the continental margin". Central to obtaining this understanding will be advances in observing and modeling the cross-shelf component of transport. More specific objectives are to understand 1) cross-margin exchanges, 2) air sea exchanges, 3) benthic-pelagic exchanges, 4) terrestrial inputs and 5) biological and chemical transformations within the water column. CoOP research will be carried out primarly through a series of process-oriented field studies, each involving about two years of measurements. Each of these field studies is to be initiated and defined through a community workshop. In addition to the process studies, CoOP will also involve modeling, long time series, exploratory studies, remote sensing, technological innovation, data archiving and communications. A CoOP pilot study has been approved for funding by the National Science Foundation, and funding will begin in 1992. The CoOP science effort is thus already underway.Funding was provided by the National Science Foundation under Grant No. OCE-9108993

Draft genome sequence of strain HIMB100, a cultured representative of the SAR116 clade of marine Alphaproteobacteria

Strain HIMB100 is a planktonic marine bacterium in the class Alphaproteobacteria. This strain is of interest because it is one of the first known isolates from a globally ubiquitous clade of marine bacteria known as SAR116 within the family Rhodospirillaceae. Here we describe preliminary features of the organism, together with the draft genome sequence and annotation. This is the second genome sequence of a member of the SAR116 clade. The 2,458,945 bp genome contains 2,334 protein-coding and 42 RNA genes