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A method of echo integration using a five criteria system
Ultrasonics International 8 7 abstracts A systematic investigation has resulted in a greater understanding of the effect of sonication on this nucleophilic displacement. Such factors as irradiation power, reaction temperature and particle size of the potassium carbonate all contribute to an overall balance in sonochemical reactivity. The results can be used to find optimum conditions for other similar reactions e.g. the O versus C alkylation reactions of 2-naphthol.
Sonochemical aspects of cell disruption by ultrasound
M.S. Palma and A.J. Bucalon, UNESP, Rio Claro, Brazil The possible mechanisms of cell disruption were analysed taking into account stable sonic cavitation phenomena at the molecular level. Saccharomyces uvarum and Candida lipolytica were irradiated with ultrasound at 20 kHz and 10 W cm 2 for various times. The cell disruption was studied in the presence and absence of the plasma membrane. Plotting the percentage of cell disruption (and survival) as a function of irradiation time, we observed multiphasic curves. After 20 min irradiation the disruption percentages for intact and permeabilized cells, respectively, were 80% and 72% for S. uvarum and 57% and 66% for C. lipolytica. The species difference in the susceptibility to cell disruption may be due to differences in chemical compositions of the cell wall. To characterize the disruption mechanism for both yeasts, we measured the quantity of hexose monomers and of broken disulfide bonds in the membrane extracts. The results suggest that thousands of chemical bonds are cleaved from each point of rupture in the wall. After 5 min irradiation we observed the appearance of a maximum in the quantity of hexose in the medium, and almost all the disulfide bonds were broken. With additional irradiation, there was a rapid decrease in the concentration of hexoses and thiol groups. These results suggest the occurrence of several chemical reactions that modify these groups during irradiation. We speculate that the above effects are promoted by the collapse of resonant microbubbles against the cellular surface, by the high density of acoustic energy, by the occurrence of local high-pressure regions and by the velocity gradient of acoustic flow. Hydrogen peroxide, which forms during sonication, may be responsible for the oxidation of a large number of molecules in the cellular extract once the cells are disrupted.
Computer analysis of various switching circuit for the two-dimensional transducers" array of a hydroacoustic imaging system
section selection). The assumption of minimal cross-talk signals and of minimal attenuation of useful signals has been tested for these different switching circuits. The basic principle of analysis is that only one transducer is active. Given this, it is easy to generalize the results due to the superposition principle which holds for invariant, linear and lumped elements. It is necessary for a designer to know the relationships between matrix size, the parameters of the transducers, the switching circuit, load resistances and cross-talk signals. The best way to ascertain these relations is computer analysis but there are no computer programs which can accept a large number of nodes. Maximum of nodes' number is limited in NODAL, NAP2, SPACE computer programs. The new computer program MATRIX was written to calculate the special coefficients of cross-talk signals and of the attenuation of the useful signals. This program performs sinusoidal steady state analysis of linear networks by the nodal method. It was assumed that analysis is carried out for the chosen frequency. During this analysis the elements of all matrix and vectors are complex numbers. Node equations are arranged automatically, by the direct construction of a nodal-admittance matrix and a courent source vector. The Gauss procedure is used to solve them: example, models of transducers and switching circuits are considered. It was shown that minimal cross-talk signals are obtained in the switching circuit with line and section selection. The effect of changes in the parameters of transducers, switching circuits, load resistances, matrix size and number of sections on cross-talk signals was examined. The relationships between different parameters and cross-talk signals were computed and the results are 3resented in the form of graphs.
A method of echo integration using a five criteria system
D. Ruser and R. Salamon, Technical University of Gdansk, Poland Target detection in the presence of noise is a continuing problem in underwater ultrasonics. The present poster presents a simulation of target detection in the presence of Gaussian noise using a variety of signal-to-noise ratios and detection thresholds. The simulation is based both on single transmissions (using 1000 repetitions) and on groups of five transmissions. The tests cover and extend the range of situations found in real echosounding conditions. The application of a newly devised system using five detection criteria is shown to increase the probability of successful detection, in particular by reducing significantly the probability of false alarms.
A. Grabowska, Technical University of Gdansk, Poland Underwater acoustic imaging systems are useful in providing underwater observation and inspection capabilities whenever optical systems fail. The purpose of underwater acoustic imaging is to produce two-dimensional images of underwater objects. The receiving transducers' array is applied to sample the input acoustical field. The samples are then transformed into electrical signal. In the systems both with a lens and electronic focussing this part between the transducers' array and other electronic circuits is referred to as the switching circuit. One of the most important problems in such systems is to choose the optimum switching circuit. This means that cross-talk signals ought to be reduced to a minimum as ought the attenuating of useful signals. The main purpose of this paper is to select the switching circuit which involves a minimum of electrical cross-talk signals. The application of the different switching circuits is discussed (a system of co-ordinates, a system of line selection, a system of line and
High power resonant horns for ultrasonic welding and their material aspects
F.F. Rawson, FFR Ultrasonics, Queniborough, UK Resonant horns used in power ultrasonic systems at 20 kHz for welding, insertion, cutting, etc., range from single halfwavelength cylinders of a few millimeters in diameter to three wavelengths in height or 100 mm diameter. Horns may also be rectangular in section with dimensions of 200 mm or more. Design of horns to give large uniform vibrational amplitudes at the working force can be complex. Also, use of shape factors in stepped horn design affects both vibrational amplitude at the working face and its uniformity. In particular the stud used to join small diameter horns has a significant effect. Design rules and parameters for such horns will be discussed with reference to recent experimental data.
Ultrasonics 1987 Vol 25 November
371
Sonochemical aspects of cell disruption by ultrasound
M.S. Palma and A.J. Bucalon, UNESP, Rio Claro, Brazil The possible mechanisms of cell disruption were analysed taking into account stable sonic cavitation phenomena at the molecular level. Saccharomyces uvarum and Candida lipolytica were irradiated with ultrasound at 20 kHz and 10 W cm 2 for various times. The cell disruption was studied in the presence and absence of the plasma membrane. Plotting the percentage of cell disruption (and survival) as a function of irradiation time, we observed multiphasic curves. After 20 min irradiation the disruption percentages for intact and permeabilized cells, respectively, were 80% and 72% for S. uvarum and 57% and 66% for C. lipolytica. The species difference in the susceptibility to cell disruption may be due to differences in chemical compositions of the cell wall. To characterize the disruption mechanism for both yeasts, we measured the quantity of hexose monomers and of broken disulfide bonds in the membrane extracts. The results suggest that thousands of chemical bonds are cleaved from each point of rupture in the wall. After 5 min irradiation we observed the appearance of a maximum in the quantity of hexose in the medium, and almost all the disulfide bonds were broken. With additional irradiation, there was a rapid decrease in the concentration of hexoses and thiol groups. These results suggest the occurrence of several chemical reactions that modify these groups during irradiation. We speculate that the above effects are promoted by the collapse of resonant microbubbles against the cellular surface, by the high density of acoustic energy, by the occurrence of local high-pressure regions and by the velocity gradient of acoustic flow. Hydrogen peroxide, which forms during sonication, may be responsible for the oxidation of a large number of molecules in the cellular extract once the cells are disrupted.
Computer analysis of various switching circuit for the two-dimensional transducers" array of a hydroacoustic imaging system
section selection). The assumption of minimal cross-talk signals and of minimal attenuation of useful signals has been tested for these different switching circuits. The basic principle of analysis is that only one transducer is active. Given this, it is easy to generalize the results due to the superposition principle which holds for invariant, linear and lumped elements. It is necessary for a designer to know the relationships between matrix size, the parameters of the transducers, the switching circuit, load resistances and cross-talk signals. The best way to ascertain these relations is computer analysis but there are no computer programs which can accept a large number of nodes. Maximum of nodes' number is limited in NODAL, NAP2, SPACE computer programs. The new computer program MATRIX was written to calculate the special coefficients of cross-talk signals and of the attenuation of the useful signals. This program performs sinusoidal steady state analysis of linear networks by the nodal method. It was assumed that analysis is carried out for the chosen frequency. During this analysis the elements of all matrix and vectors are complex numbers. Node equations are arranged automatically, by the direct construction of a nodal-admittance matrix and a courent source vector. The Gauss procedure is used to solve them: example, models of transducers and switching circuits are considered. It was shown that minimal cross-talk signals are obtained in the switching circuit with line and section selection. The effect of changes in the parameters of transducers, switching circuits, load resistances, matrix size and number of sections on cross-talk signals was examined. The relationships between different parameters and cross-talk signals were computed and the results are 3resented in the form of graphs.
A method of echo integration using a five criteria system
D. Ruser and R. Salamon, Technical University of Gdansk, Poland Target detection in the presence of noise is a continuing problem in underwater ultrasonics. The present poster presents a simulation of target detection in the presence of Gaussian noise using a variety of signal-to-noise ratios and detection thresholds. The simulation is based both on single transmissions (using 1000 repetitions) and on groups of five transmissions. The tests cover and extend the range of situations found in real echosounding conditions. The application of a newly devised system using five detection criteria is shown to increase the probability of successful detection, in particular by reducing significantly the probability of false alarms.
A. Grabowska, Technical University of Gdansk, Poland Underwater acoustic imaging systems are useful in providing underwater observation and inspection capabilities whenever optical systems fail. The purpose of underwater acoustic imaging is to produce two-dimensional images of underwater objects. The receiving transducers' array is applied to sample the input acoustical field. The samples are then transformed into electrical signal. In the systems both with a lens and electronic focussing this part between the transducers' array and other electronic circuits is referred to as the switching circuit. One of the most important problems in such systems is to choose the optimum switching circuit. This means that cross-talk signals ought to be reduced to a minimum as ought the attenuating of useful signals. The main purpose of this paper is to select the switching circuit which involves a minimum of electrical cross-talk signals. The application of the different switching circuits is discussed (a system of co-ordinates, a system of line selection, a system of line and
High power resonant horns for ultrasonic welding and their material aspects
F.F. Rawson, FFR Ultrasonics, Queniborough, UK Resonant horns used in power ultrasonic systems at 20 kHz for welding, insertion, cutting, etc., range from single halfwavelength cylinders of a few millimeters in diameter to three wavelengths in height or 100 mm diameter. Horns may also be rectangular in section with dimensions of 200 mm or more. Design of horns to give large uniform vibrational amplitudes at the working force can be complex. Also, use of shape factors in stepped horn design affects both vibrational amplitude at the working face and its uniformity. In particular the stud used to join small diameter horns has a significant effect. Design rules and parameters for such horns will be discussed with reference to recent experimental data.
Ultrasonics 1987 Vol 25 November
371