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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 25 out of 330
Title |
Absorption of ultrasonic waves in aqueous solutions of biopolymers. |
Author |
Sadykhova SK, El?piner IE. |
Journal |
Sov Phys Acoust |
Volume |
|
Year |
1970 |
Abstract |
A pulsed ultrasonic apparatus has been used to investigate the attenuation of ultrasound in aqueous solutions of proteins and nucleic acids in the frequency interval from 12 to 68 Mc. A relationship is established between the absorption coefficient and conformational characteristics of the investigated biopolymers. Muscle and globular proteins (actin, myosin, actomyosin, and serum albumin) are differentiated according to their ultrasonic absorption in the indicated frequency interval. It is found that the modification induced in the conformation of the biopolymer ribonucleic acid (RNA) by interaction with formaldehyde and hydroxylamine increases the absorption. Alkali hydrolysis, the action of high-intensity ultrasound, or the presence of urea in the solution, on the other hand, is accompanied by a reduction in the absorption coefficient. |
Title |
Absorption of ultrasound by mammalian ovaries. |
Author |
Carnes KI, Dunn F. |
Journal |
J Acoust Soc Am |
Volume |
|
Year |
1988 |
Abstract |
The transient thermoelectric method was employed to determine the ultrasonic absorption coefficient of excised bovine, canine, feline, murine, ovine, and porcine ovaries at 1 MHz. The dynamics of the organ yields significant variations with physiological stage and structure. Values ranged from 0.017 cm-1 for the follicle to 0.050 cm-1 for the corpus luteum, largely reflecting macromolecular content. Little interspecies variation was observed. |
Title |
Absorption of ultrasound by normal and pathological human gonadal tissues in vitro. |
Author |
Inoue H, Carnes KI, Dunn F. |
Journal |
Jpn J Med Ultrason |
Volume |
|
Year |
1993 |
Abstract |
The transient thermoelectric method was employed to determine the ultrasonic absorption coefficient a of normal and pathological excised human ovary and testis at 1 and 3.25 MHz. At 1 MHz, a of normal ovary ranged from 0.016 for follicle to 0.046 Np/cm for the tunica albuginea, while the studied pathologies ranged from 0.02 to 0.123 Np/cm. The a increased from 0.018 Np/cm for normal testis from 0.024 to 0.048 Np/cm for the pathological organs studied. The observed changes in the absorption coefficient, of the pathologies from normal, are consistent with the attending changes in water and protein content. The frequency dependence for testis is f(1.4) and increases with the studied pathologies, while that for ovary is f(1.6) and decreases with the studied pathologies. |
Title |
Absorption of ultrasound by tissues and biological matter. |
Author |
Schwan HP. |
Journal |
Proc IRE |
Volume |
|
Year |
1959 |
Abstract |
General principles which determine the frequency dependence of both absorption and velocity of ultrasound in matter are outlined and applied to cell suspensions and tissues. The mechanisms which are responsible in the biological case for the experimentally observed frequency dependence of ultrasonic properties are described. They relate predominantly to macromolecular components. Finally, the relationships which pertain to the propagation of ultrasound in heterogeneous tissue complexes are discussed, and consequences for the medical application as a therapeutic tool are considered. |
Title |
Absorption of ultrasound in binary solutions of polyacrylamide with water. |
Author |
Haque MF, Fast SJ, Yun SS, Stumpf FB. |
Journal |
J Acoust Soc Am |
Volume |
|
Year |
1985 |
Abstract |
The absorption coefficient of ultrasound and shear viscosity in binary solutions of polyacrylamide with water were studied as a function of concentration and temperature. In addition, the absorption coefficient was measured as a function of frequency. The value of alpha/f2 increased by twofold, at 3% concentration and 20 degrees C, from the water value while the shear viscosity increased by four orders of magnitude. The temperature dependence of alpha/f2 for the polymer solutions is similar to that of pure water. |
Title |
Absorption of ultrasound in biological media. |
Author |
Dunn F, Brady JK. |
Journal |
Biofizika |
Volume |
|
Year |
1973 |
Abstract |
Measurements have been made of the linear absorption coefficient of ultrasound in tissues of the c.n.s. of mammals over the temperature range from 0 to 50 degrees C of 0-5, 0-7, and 1.0 Mc/s. The spinal cord of newborn mice (24 hr. after birth) is a convenient object for the investigation. The character of the change in absorption is similar to changes found close to the main relaxation frequencies in highly viscous fluids. |
Title |
Absorption of ultrasound in biomolecular solutions. |
Author |
Kremkau FW, Hantgan RR. |
Journal |
Proc Ultrason Symp IEEE |
Volume |
|
Year |
1988 |
Abstract |
Absorptions of albumin in four buffers indicate that their presence affects absorption (supporting a solvation mechanism). Proline, bacitracin, hemoglobin, and three synthetic phosphatidyl choline lipids all have increased absorption in organic solvents. Absorption for protein mixtures at pH?s where one molecule has negative net charge while the other has positive do not indicate a relevant role for electrostatic interactions in absorption. Glutaraldehyde polymerization of an albumin solution caused no change in absorption. Lipid absorption measurements support interaction observations with proteins. From these results it is concluded that molecular size, structure, solvation, and solute interactions are relevant factors in the absorption of ultrasound in biological material. |
Title |
Absorption of ultrasound in liquid NH(3) and ND(3). |
Author |
Bowen DE. |
Journal |
J Chem Phys |
Volume |
|
Year |
1973 |
Abstract |
Data on the absorption of ultrasound in liquid NH(3) and ND(3) as a function of frequency and temperature are presented. These data indicate that the absorption is both frequency and temperature independent for frequencies above 30 MHz at a value two times the classical value. There is a relaxation occurring at the lower frequencies indicated by an increase in the absorption coefficient as the frequency is lowered. This is interpreted to be a thermal relaxation and not a structural relaxation, which is what might be expected for an associated liquid such as NH(3). |
Title |
Acceleration of bone repair by pulsed sine wave ultrasound: animal, clinical and mechanistic studies. |
Author |
Pilla AA, Flgueiredo M, Nasser P, Alves JM, Ryaby JT, Klein M, Kaufman JJ, Siffert RS. |
Journal |
Electromagnetics Bio Med |
Volume |
|
Year |
1991 |
Abstract |
No abstract available. |
Title |
Accuracy calculations for ultrasonic pulsed doppler blood flow measurements. |
Author |
Gill RW. |
Journal |
Australas Phys Eng Sci Med |
Volume |
|
Year |
1982 |
Abstract |
A technique has been developed, based on the concept of uniform insonification, for the noninvasive measurement of blood flow using pulsed Doppler and B-mode ultrasound. Previously reported in vitro tests have confirmed the validity of the method, and have shown errors which are consistent with those theoretically expected due to uncertainties in measuring the mean Doppler shift, the angle of approach of the ultrasound beam to the vessel, and the area of the vessel's lumen. Analysis has also been made of the errors introduced by high-pass filtering of the Doppler signal (to reject wall and tissue movement), interfering electrical and flow signals, and crosstalk in the Doppler signal processing. The work reported in this paper extends the analysis of accuracy by considering both the degree to which the assumption of uniform scattering is satisfied and the effects of non-uniform scattering on the flow measurement. |
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