Daniels S, Blondel D, Crum L A, ter Haar G R, Dyson M
Oxford Hyperbaric Group, Physical Chemistry Laboratory, London.
Ultrasound Med Biol. 1987 Sep;13(9):527-39. doi: 10.1016/0301-5629(87)90179-7.
Macroscopically visible gas bubbles can be produced in an agar based gel by irradiation with either continuous or pulsed ultrasound at frequencies from 0.75 to 3.0 MHz. The variation in the number of bubbles formed with frequency, acoustic pressure, pulse length, duty cycle, and temperature closely resembles that seen in vivo. Furthermore, the acoustic pressure required to initiate bubble formation is also close to that required in vivo. It has been observed that alterations in the concentration and pH of the gels can have a profound effect on the nature and quantity of bubbles. This suggests that not only is this gel model suitable for the representation of the macroscopic features of bubble formation in vivo, but can be used to gain information about the preexisting bubble nuclei. Based on the experimental results obtained it can be suggested that for peak negative acoustic pressures of up 1 MPa (equivalent, for a plane travelling sinusoidal wave, to a time averaged intensity of 30 W/cm2) bubble formation can be avoided by the use of high frequencies, short pulse lengths and long duty cycles.
通过使用频率在0.75至3.0MHz之间的连续或脉冲超声照射琼脂基凝胶，可以产生肉眼可见的气泡。形成的气泡数量随频率、声压、脉冲长度、占空比和温度的变化，与体内观察到的情况极为相似。此外，引发气泡形成所需的声压也与体内所需的声压相近。据观察，凝胶浓度和pH值的变化会对气泡的性质和数量产生深远影响。这表明，这种凝胶模型不仅适用于呈现体内气泡形成的宏观特征，还可用于获取有关预先存在的气泡核的信息。基于所获得的实验结果，可以提出，对于高达1MPa的负峰值声压（对于平面传播的正弦波，相当于时间平均强度为30W/cm²），通过使用高频、短脉冲长度和长占空比可以避免气泡形成。
