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Sound Velocity (sound + velocity)

Distribution by Scientific Domains
Medical Sciences33%

Selected Abstracts

How correct is the EOS of weakly nonideal hydrogen plasmas?

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2003
A.N. Starostin
Abstract Helioseismology opens new possibility to check EOS of weakly nonideal hydrogen plasmas with high precision, using reconstructed local sound velocities within 10-4 accuracy. A comparison of different theoretical models with experiment permits to verify the existing methods of calculation bound states and continuum contribution to the second virial coefficient within the framework of physical nature. The regular way of the deduction expression for EOS is presented and generalization of the EOS for broad atomic states and two temperature non-equilibrium case is proposed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Determination of elastic modulus of demineralized resin-infiltrated dentin by self-etch adhesives

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2007
Genta Yasuda
The purpose of this study was to determine ultrasonically the changes in elastic modulus of demineralized adhesive-infiltrated dentin. Dentin disks were obtained from bovine incisors and shaped into a rectangular form. The specimens were immersed in single-step self-etch adhesives, then stored in distilled water and run through thermal cycles between 5 and 60°C. The longitudinal and shear wave sound velocities and the elastic modulus were determined using ultrasonic equipment composed of a pulser-receiver, transducers, and an oscilloscope. After 24 h of storage, the elastic modulus of mineralized dentin was 16.9 GPa and that of demineralized dentin was 2.1 GPa. The immersion of demineralized dentin in adhesives significantly increased the elastic modulus to 3.3,5.9 GPa. After 30,000 thermal cycles, the elastic modulus of dentin was 32.4 GPa, whereas that of demineralized adhesive infiltrated dentin was 3.1,4.1 GPa. Thermal stresses did not cause adhesive-infiltrated demineralized dentin to deteriorate, as measured by elastic modulus. [source]

Presheath in Fully Ionized Collisional Plasma in a Magnetic Field

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
B. Alterkop
Abstract The quasineutral presheath layer at the boundary of fully ionized, collisional, and magnetized plasma with an ambipolar flow to an adjacent absorbing wall was analyzed using a two fluid magneto-hydrodynamic model. The plasma is magnetized by a uniform magnetic field B, imposed parallel to the wall. The analysis did not assume that the dependence of the particle density on the electric potential in the presheath is according to the Boltzmann equilibrium, and the dependence of the mean collision time , on the varying plasma density within the presheath was not neglected. Based on the model equations, algebraic expressions were derived for the dependence of the plasma density, electron and ion velocities, and the electrostatic potential on the position within the presheath. The solutions of the model equations depended on two parameters: Hall parameter (, ), and the ratio (, ), where , = ZTe /(ZTe + Ti ), and Te , Ti and Z are the electron and ion temperatures and ionicity, respectively. The characteristic scale of the presheath extension is several times ri /, , where ri is the ion radius at the ion sound velocity. The electric potential could have a non monotonic distribution in the presheath. The ions are accelerated to the Bohm velocity (sound velocity) in the presheath mainly near the presheath-sheath boundary, in a layer of thickness ,ri /, . The electric field accelerates the ions in the whole presheath if their velocity in the wall direction exceeds their thermal velocity. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Development and Evaluation of an Ultrasonic Ground Water Seepage Meter

GROUND WATER, Issue 6 2001
Ronald J. Paulsen
Submarine ground water discharge can influence significantly the near-shore transport and flux of chemicals into the oceans. Quantification of the sources and rates of such discharge requires a ground water seepage meter that provides continuous measurements at high resolution over an extended period of time. An ultrasonic flowmeter has been adapted for such measurements in the submarine environment. Connected to a steel collection funnel, the meter houses two piezoelectric transducers mounted at opposite ends of a cylindrical flow tube. By monitoring the perturbations of fluid flow on the propagation of sound waves inside the flow tube, the ultrasonic meter can measure both forward and reverse fluid flows in real time. Laboratory and field calibrations show that the ultrasonic meter can resolve ground water discharges on the order of 0.1 ,m/sec, and it is sufficiently robust for deployment in the field for several days. Data from West Neck Bay, Shelter Island, New York, elucidate the temporal and spatial heterogeneity of submarine ground water discharge and its interplay with tidal loading. A negative correlation between the discharge and tidal elevation was generally observed. A methodology was also developed whereby data for the sound velocity as a function of temperature can be used to infer the salinity and source of the submarine discharge. Independent measurements of electrical conductance were performed to validate this methodology. [source]

Photoacoustic monitoring of neovascularities in grafted skin

LASERS IN SURGERY AND MEDICINE, Issue 3 2006
Mutsuo Yamazaki MS
Abstract Background and Objective In skin grafting, evaluation of graft adhesion to the recipient site in the early postgrafting period is important. However, conventional diagnoses such as visual observation and thermography required about 1 week to obtain results and these methods cannot give quantitative information on the adhesion of a skin graft. We proposed a new method for monitoring adhesion of grafted skin that is based on measurement of photoacoustic signals. To investigate the validity of the method, we performed experiments using rat autografts models. Study Design/Materials and Methods Grafted skin in a rat was irradiated with 200 µJ, 532-nm nanosecond laser pulses, and photoacoustic signals were detected with a piezoelectric transducer placed on the skin at various postgrafting time. Temporal profiles of the signals were converted to depth profiles using an assumed sound velocity of 1,500 m/second. Histological analysis was performed to observe neovascularities formed in the grafts. Results At 6 hours postgrafting, a photoacoustic signal peak appeared in the depth region corresponding to the graft. The results of histological analysis also showed formation of neovascularities in the graft after 6 hours postgrafting, indicating that photoacoustic signal peaks observed in the graft originated from the neovascularities, which are an indication of graft adhesion. For up to 24 hours postgrafting, no significant difference was observed between the results of visual observation and laser Doppler imaging of the same grafted skins. Conclusion We have demonstrated that photoacoustic signals originating from neovascularities in grafts can be sensitively detected in the early postgrafting period, suggesting the validity of photoacoustic measurement for adhesion monitoring of skin grafts. Lasers Surg. Med. 38:235,239, 2006. © 2006 Wiley-Liss, Inc. [source]