Acoustic method

The propagation of small pressure pulses or sound waves is a physical effect which can be a source of information for single and multiphase systems. Ultrasonic methods (between 20 kHz and 100 MHz) are easy to use, safe, non-destructive and non-invasive. MorbideUi et al. [19] used this acoustic method, with success, for the determination of the evolution of conversion in various copoly-meric systems in the dispersed phase (emulsion polymerization). The same methodology has been applied to bulk and solution systems by Gavin et al. [20, 21] and Zeihnann et al. [22] for monitoring high-soUds content polymerization of styrene and MM A. 

Changes in resonant freqnency measnred as a fnnction of time can be linked to the adsorption of a molecnlar layer on a qnartz snbstrate and is related to changes in the thickness of the layer. In the case of pnre adsorption, the decrease in resonant freqnency is connected with an increase in the layer thickness, as follows A/ = where v is the speed of the transverse wave in 

In the simplest format, usually only the series resonant frequency is measured. This method, known as quartz crystal microbalance (QCM), was developed by Sauerbrey (1959), who derived a relation between changes in resonant frequency, Afs, and changes in the surface mass density, p  

In its simplest, QCM, format, protein-aptamer interactions were analyzed by Liss et al. (2002). They compared the interaction of IgE with DNA aptamer as well as with anti-IgE antibodies. Although the detection limit was similar in the two cases, the advantage of the aptasensor was its possibility of surface regeneration, which was impossible for an antigen-based biosensor. However, recently it has been shown that immobilization of anti-IgE on the dendrimer surface also allows us to regenerate an immunosensor (Svobodova et al., 2006). The QCM method was recently compared with the electrochemical biosensor assay of thrombin detection (Hianik et al., 2005, 2007). It has been shown that the sensitivity of thrombin detection was similar for the two methods. Mascini and co-workers showed that similar results in sensitivity and selectivity in the detection of Tat peptide with RNA aptamer can be obtained by the QCM and SPR methods (Tombelli et al., 2005b). 

Recently, we applied the TSM sensor for the characterization of all steps in the sensor fabrication and detection of thrombin-aptamer interactions (Grman et al., 

According to the Sauerbrey equation [equation (5.1)], from changes in fs it is possible to calculate the change of mass. Am, at the device surface, and from the known molecular mass (MW) of neutravidin (60 kDa) the number of 

The variation of sound velocity with cyclic frequency, to (= 2 a/), is given by 

The variation with frequency of the sound absorption coefficient, p, which rises to a maximum in the centre of the dispersion zone, is given by 

This gives the curve shown in Fig. 1 (b), and relaxation times may also be estimated by fitting sound absorption measurements, corrected for classical absorption, to the appropriate theoretical curve. 

Measurements of sound velocity at ultrasonic frequencies are usually made by an acoustic interferometer. An example of this apparatus11 is shown in Fig. 2. An optically flat piezo-quartz crystal is set into oscillation by an appropriate electrical circuit, which is coupled to an accurate means of measuring electrical power consumption. A reflector, consisting of a bronze piston with an optically flat head parallel to the oscillating face of the quartz, is moved slowly towards or away from the quartz by a micrometer screw. The electrical power consumption shows successive fluctuations as the distance between quartz and reflector varies between positions of resonance and non-resonance of the gas column. Measurement of the distance between resonance positions gives a value for A/2, and if / 

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I.E. Kurov, G.B. Muravin, A.V. Mochovich. Research of the destruction development in carbon plastic by mechanical and acoustic methods. 

The solution of this task results in the possibility to apply more efficient acoustic methods for investigation and diagnostics of engineering materials and weld condition. 

Lange, Yu V. Low Frequency Acoustic Methods and Means for Nondestructive. Testing of Multilayer Structures. Moscow, Mashinostrojenije, 1991, 272 p. (in Russian)... 

The direction of orientation in HDPE film and the orientation degree can be determined by either the x-ray method, ir polarization spectroscopy, acoustical methods, or birefringence (21,22,120,121). 

As mentioned above, the numerical solution of exact equations breaks down for low flame speeds, where the strength of the leading shock approaches zero. To complete the entire range of flame speeds, Kuhl et al. (1973) suggested using the acoustic solutions by Taylor (1946) as presented earlier in this section. Taylor (1946) already noted that his acoustic approach is not fully compatible with the exact solution, in the sense that they do not shade into one another smoothly. In particular, the near-piston and the near-shock areas in the flow field, where nonlinear effects play a part, are poorly described by acoustic methods. In addition to these imperfections, the numerical character of Kuhl etal. (1973) method inspired various authors to design approximate solutions. These solutions are briefly reviewed. 

These findings qualitatively confirm the results obtained with the simple acoustic methods, discussed previously. 

Example 13-3. Sizing a Pulsation Dampener Using Acoustic Method... 

Storer model used in this theory enables us to describe classically the spectral collapse of the Q-branch for any strength of collisions. The theory generates the canonical relation between the width of the Raman spectrum and the rate of rotational relaxation measured by NMR or acoustic methods. At medium pressures the impact theory overlaps with the non-model perturbation theory which extends the relation to the region where the binary approximation is invalid. The employment of this relation has become a routine procedure which puts in order numerous experimental data from different methods. At low densities it permits us to estimate, roughly, the strength of collisions. 

Let us note that cross-sections aE, obtained from optical data and verified by NMR measurements, exceed the corresponding cross-sections found by acoustic methods (c 4 3 A2) [168]. A similar disagreement between the data obtained by NMR and molecular spectroscopy with the acoustic data exists for linear molecules as well. 

Other devices and methods can also be applied, such as laser interferometry, which measures the change in the height of fuel in the tank using lasers, or acoustics methods that measure the sound of fluid escaping or entering the tank. 

Acoustic emission (AE) technique, in nondestructive evaluation, 17 425 Acoustic fields, filtration and, 11 324 Acoustic methods, of emulsion characterization, 10 128 Acoustic microscope, 16 505... 

Acoustic methods Active or passive X Solid, semisolid, and high viscose sample High shear granulation monitoring Crystallization monitoring... 

Max Bender, MP 38, 109-28(1956) (Examination of Dynamite cartridges by acoustic method in order to determine the stare of deterioration)... 

It is thus more difficult to investigate experimentally by acoustic methods, which will require very high fjp values at which classical dispersion and absorption must also be taken into account87. Theoretical treatment is also much less satisfactory molecules are usually distributed in a variety of rotational energy levels, so that a number of different transition probabilities have to be considered, and observed relaxation times usually represent averages over sets of transitions involving a range of /-states. 

In addition to acoustical methods, which take advantage of the fact that gas nuclei (i.e., stable microbubbles) are elastic bodies and thus absorb sound energy (ref. 4,5,9,25,26,31,32,50), another class of methods for detecting these gas microbubbles that has been employed repeatedly is based on their optical behavior. Specifically, most of these optical methods involve detection of these long-lived microbubbles in water from the light scattered by them (ref. 5,26,59,60,127). 

FTIR reflectance and transmission spectroscopy is used for analysis of thin films. Nevertheless, due to the high absorptivities of mid-IR bands, the film thickness must be limited (up to 100 pm, depending on the specific bands chosen) in order to perform an accurate qualitative analysis. Other IR methods, such as attenuated total reflectance (ATR) and photoacoustic methods provide IR spectra of thick material, because they penetrate a very thin layer at the surface of a sample. However, is important to point out that the effective pathlength for the ATR and the photo-acoustic methods depends on the refractive index and thermal diffusivity, respectively. Therefore, the use of these techniques for the quantitative analysis of non-homo-geneous materials can be difficult. 

First, due to some approaching we have obtained non-linear periodical wave functions of electron ion carbon nanotubes, which are presented soliton lattices. We consider soliton lattices of obtained type can be revealed by using the diffraction methods. The research based on these methods will make it possible to determine the parameters of the grids and connect them to the corresponding values in microscopic Hamiltonian. Besides these lattices can modulate sound fluctuations, that it is also necessary to take into account at the study of nanotubes by acoustic methods. 

C02 in the gas phase can be determined by means of its significant infrared absorbance (Fig. 10) at wave lengths (A) < 15 pm, particularly at 4.3 pm [289], or by acoustic means. Integrated photoacoustic spectroscopy and magnetoacoustic (PAS/MA) technology for combined C02 and 02 analysis has rapid response time and a small sample volume is sufficient. The acoustic methods are accurate, stable over long periods and very simple to use. 

Thus, we have been able to estimate the strength of the interaction between solvent and CD molecules with the aid of NMR, and the number of solvating solvent molecules with the acoustic method. 

Malinauskas and co-workers [204, 205] and also Healy and Storvich [206] have derived rotational collision numbers from thermal transpiration measurements, utilizing the theory developed by Mason and co-workers [149]. Values have been obtained for the gases N2, CO, 02, and C02, up to temperatures of 500°K. Collision numbers were also obtained by Healy and Storvick for H2 at 444° and for CH4 and CF4 at 366°K. The latter three cases present difficulties for this technique, and it could only be ascertained that Zr(H2) is greater than 100. For N2, 02, and C02, the values of Zr obtained were in good agreement with those derived from acoustical methods, except that the increase in Zr with increasing temperature appeared more pronounced for the thermal transpiration method. 

Acoustic methods offer several advantages when compared to other comparable techniques (1) applicable to concentrated suspensions (2) less sensitive to particulate contamination (3) better suited to polydisperse suspensions (4) applicable to a wide size range (5) well suited to automated potentiometric titrations and analysis... 

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