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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 106 out of 330
| Title |
Effects of random deviations in interface properties on the propagation of ultrasound in thick composites. |
| Author |
Lu Y, Achenbach JD. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1991 |
| Abstract |
Propagation of ultrasound across a solid layer with equally spaced parallel interfaces is studied by using a transfer matrix method. For a layer with identical interfaces the propagation of ultrasound is governed by a dispersion relation, which displays passing and stopping bands in the frequency domain. For a layer with interfaces that have random deviations from mean interface properties, the Furstenberg theorem and Monte Carlo simulation have been used to study propagation of ultrasound across the layer. It has been shown that at all frequencies there is and exponential decay in the amplitude of the transmitted wave. This decay, which increases with increasing frequency, defines a localization phenomenon, since wave motion will be confined to the insonified side of the layer. |
| Title |
Effects of short-duration exposures to 2MHz ultrasound on growth and mitotic index of Pisum sativum roots. |
| Author |
Miller MW, Kaufman GE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1977 |
| Abstract |
Roots of Pisum sativum were exposed to 2 MHz ultrasound for durations from 0.006 to 60 sec. Growth was noticably reduced by exposure durations of 0.03 sec and longer (at a spatial peak intensity of 20 w/cm2) and mitotic index was noticably depressed by exposure durations of 0.06 sec and longer (at 30 W/cm2). Additional increments of ultrasound exposure were progressively less effective in further reducing growth and mitotic index. Thus, a major part of the damage from a one-minute ultrasound exposure appears to be produced within the first few seconds after the beam is turned on. |
| Title |
Effects of therapeutic ultrasound on bone marrow in dogs. |
| Author |
Payton OD, Lamb RL, Kasey ME. |
| Journal |
Phys Ther |
| Volume |
|
| Year |
1975 |
| Abstract |
No abstract available. |
| Title |
Effects of therapeutic ultrasound on clearance rate of blood borne colloidal particles in vivo. |
| Author |
Saad AH, Williams AR. |
| Journal |
Br J Cancer Suppl |
| Volume |
|
| Year |
1982 |
| Abstract |
No abstract available |
| Title |
Effects of therapeutic ultrasound on the activity of the mononuclear phagocyte system in vivo. |
| Author |
Saad AH, Williams AR. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1986 |
| Abstract |
Therapeutic intensities of continuous wave ultrasound applied over the umbilical area of female rats resulted in a decrease in the rate of removal of 99mtechnetium radio-labelled sulphur colloid by the mononuclear phagocyte system. The magnitude of this effect increased both with increasing intensity of ultrasound and with the duration of exposure, and was found to be dependent upon the total amount of energy deposited within the umbilical area. This effect appeared to be initiated by an effect of ultrasound upon circulating lymphocytes since isolated lymphocytes sonicated in vitro at therapeutic intensities and then injected intravenously resulted in a decrease in the rate of colloid removal in vivo similar to that observed when the umbilical area had been sonicated in vivo. The mechanism by which this is thought to occur is discussed. |
| Title |
Effects of ultrasonic attenuation on the accuracy of the blood flow measurement technique utilizing time domain correlation. |
| Author |
Suorsa VT, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1988 |
| Abstract |
By utilizing time domain correlation, the volumetric flow in a vessel can be estimated accurately without deteriorating effects due to the frequency-dependent attenuation of ultrasound. When the transmitted pulses are separated by a known time and are reflected by the moving scatterers within the ultrasound beam, the time difference between the pulses changes. The observed time shift is directly related to the radial speed (relative to the beam axis) of the scatterers. If the flow velocity is sampled at different positions across the vessel, then the volume flow rate can be calculated. The time domain technique has been verified in a blood flow phantom using a blood mimicking substance and natural sponge as attenuating medium between the transducer and the vessel. For hydrodynamically determined flow rates from 50 to 560 ml/min, the continuous volumetric flow has been ultrasonically assessed with an accuracy better than 21%. |
| Title |
Effects of ultrasonic irradiation on hemoglobin. |
| Author |
Weissler A |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1960 |
| Abstract |
Oxyhemoglobin in dilute aqueous solution is rapidly converted by ultrasonic irradiation into methemoglobin, which in turn is gradually destroyed, as shown by the disappearance of its optical absorption peak at 4050 A. Hematoporphyrin similarly suffers partial destruction by ultrasound. On the basis of experiments in various chemical environments, the previous results are ascribed largely to the nitrous and nitric acids produced by ultrasonic cavitation in water containing dissolved air. Adding 0.1 ml ether/25 ml of solution causes the sonochemical change to be from oxyhemoglobin into carboxyhemoglobin, instead of into methemoglobin. Ultracentrifuge studies indicate that ultrasonic treatment of hemoglobin in more concentrated solution also causes some splitting off of the heme from the globin. A comparison of the reported effects of x-rays on hemoglobin with those found for ultrasound shows that there are differences as well as similarities. The ultrasonic frequency used was 400 kc per sec, and the acoustic power delivered into the reaction vessel in a focused beam was about 20 w. |
| Title |
Effects of ultrasonic radiation in experimental focal epilepsy in the cat. |
| Author |
Manlapaz JS, Astrom KE, Ballantine HT Jr, Lele PP. |
| Journal |
Exp Neurol |
| Volume |
|
| Year |
1964 |
| Abstract |
Experimental focal epilepsy was induced in thirty-seven cats by subcortical injection of 0.1 ml of alumina cream. Fifteen of these were treated by surgical removal of the epileptogenic focus, twelve by irradiation with focused ultrasound, and nine with medication. One died before any therapy could be instituted. Ultrasonic irradiation effectively relieved the animals of the seizures and abnormal EEG patterns by eradication of the epileptogenic focus with less untoward effects and postoperative complications than did surgery. Medical therapy was ineffective. Post-mortem examination of the brains showed grossly that ultrasonic irradiation eradicated the epileptogenic focus without destroying extensively the overlying and adjacent brain tissue and without forming corticodural adhesions. Microscopically, irradiated foci could be distinguished from the surgically treated ones by inter alia absence of trabeculated loose vascular scar tissue and paucity of fibroblasts and collagen fibers. |
| Title |
Effects of ultrasound and 1,25-dihydroxyvitamin D3 on growth factor secretion in co-cultures of osteoblasts and endothelial cells. |
| Author |
Ito M,Azuma Y,Ohta T,Komoriya K. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2000 |
| Abstract |
It has been shown that low-intensity pulsed ultrasound (US) accelerates fracture healing in animal models and in clinical studies. However, the mechanism by which US accelerates fracture healing remains unclear. Systemic factors and several growth factors, such as platelet-derived growth factor (PDGF), are thought to be involved in the process of fracture healing. In the present study, we examined the effects of US and 1,25-dihydroxyvitamin D3[1,25-(OH)2D3] on growth factor secretion in a co-culture system of human osteoblastic cells (SaOS-2) and endothelial cells (HUVEC). US was applied to cultured cells for 20 min daily for four consecutive days. US treatment increased the PDGF-AB level in the conditioned media. 1,25-(OH)2D3 (1 × 10−8 M) also enhanced PDGF-AB secretion. The secretion of PDGF-AB was synergistically increased by the combination of US and 1,25-(OH)2D3. These results suggest that the stimulation of growth factor secretion from cells by US and 1,25-(OH)2D3 treatment may be involved in the acceleration of fracture healing.
Keywords: Low-intensity pulsed ultrasound; Fracture healing; 1,25-(OH)2D3; SaOS-2; HUVEC; Growth factor
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| Title |
Effects of ultrasound exposure on pregnancy: a study in the mouse. |
| Author |
Fry FJ. |
| Journal |
IEEE Trans Ultrason Ferroelectr Freq Control |
| Volume |
|
| Year |
1986 |
| Abstract |
No abstract available. |
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