Ultrasonic Spectroscopy Research Articles

Application of high-resolution ultrasonic spectroscopy for detection of the plasmin activity toward β-casein

High-resolution ultrasonic spectroscopy (HR-US) was applied for precise detection of plasmin activity towards β-casein in buffer at pH 7.8 and 37 °C. The evolution of ultrasonic velocity and ultrasonic attenuation measured at 15.5 MHz is related to the concentration of peptide bonds hydrolyzed and loss of β-casein aggregates, respectively. The ultrasonic assay presents sensitive and direct activity-based quantification of plasmin levels in milk. The variation in plasmin concentration between HR-US and ELISA method owed to the differing detection principles. The real-time ultrasonic profiles of hydrolysis were utilized to describe the kinetic aspect of plasmin activity. The non-linear activity curve was fitted with classic and inverse Michaelis–Menten type models. Within 1–8.6 mg·mL−1 β-casein, the Vmax and KM obtained were (6.30 ± 2.21) × 10−5 mol.kg−1·min−1 and 10.33 ± 3.50 mg·mL−1, respectively. The maximum peptide bond cleaved was 5–6 (2.7% degree of hydrolysis) achieved at 1 mg·mL−1 β-casein.

Disentangling proton-transfer and segmental motion relaxations in poly-vinyl-alcohol aqueous solutions by means of ultrasonic relaxation spectroscopy

A detailed temperature- and concentration-dependent ultrasonic relaxation study has been conducted in aqueous polyvinyl alcohol (PVA) solutions as a function of frequency under isobaric conditions. Concentration and temperature have similar effect on acoustic spectra. Two well-resolved relaxation processes were observed in the experimental acoustic spectra that seem to follow a Cole-Cole distribution function. The systematic analysis of the variation of the acoustic parameters with frequency, temperature and concentration revealed that both processes have collective and not local nature. The low-frequency relaxation mechanism is assigned to segmental motions of the polymer chains and the high-frequency relaxation to proton-transfer reaction, respectively. The characteristic relaxation frequencies were found independent of molecular weight, as expected for relative flexible vinyl-polymer chains with molecular weight above ~104. Based on Eyring's theory, the activation enthalpy of the low- and high-frequency relaxation were estimated equal to ΔΗ1* = 4.5 ± 0.2 kcal/mol and ΔΗ2* = 19.7 ± 0.8 kcal/mol, respectively. The contribution of the low-frequency lying normal mode relaxation has been quantitatively estimated in the context of relevant theories of the field and found almost four order of magnitude lower in amplitude compared to segmental motion process indicating that the experimentally detected relaxation is dominated by the latter. The experimental results were complemented with molecular mechanics calculations performed in parallel. The comparison between the experimental data and the outcome of the theoretical calculations evidenced that the length of the relaxing element in a PVA polymer chain is between 5 and 8 monomers in agreement with what is expected for vinyl-polymers and established the local segmental motions of the PVA polymer chains in the solution.

Linear and nonlinear resonant ultrasonic techniques applied to assess delayed ettringite formation on concrete samples

This study investigates the application of different ultrasonic Non-Destructive tests to assess Delayed Ettringite Formation, in concrete samples exhibiting low kinetic expansions (and up to 0.21%). Linear and nonlinear Resonant Ultrasonic Spectroscopy and Acoustic Emission tests were used. Scanning Electron Microscopy and optical microscopy observations were conducted at the end of the monitoring tests. The results showed a slight increase of the dynamic modulus and Quality factor while nonlinear hysteretic parameters remained constant over the test duration. Acoustic Emission tests attested the occurrence of events. However, the microscopic observations did not reveal meaningful differences in microcracking extent between the samples.

Investigation of complex fluids characterization through ultrasonic spectroscopy

Investigation of complex fluids characterization through ultrasonic spectroscopy

Dielectric, elastic and piezoelectric properties of single domain Pb(Zn1/3Nb2/3)O3–6.5%PbTiO3 single crystal with 3m symmetry measured using one sample

In order to use finite element simulation to design electromechanical devices, self-consistent full tensor material properties are needed. The IEEE resonance technique usually requires more than 5 different geometry samples to complete the full tensor characterization, but the poling degree will depend on the sample geometry in relaxor-base ferroelectric single crystals. Hence, it is very difficult to obtain self-consistent full tensor properties using multiple samples. In this study, we used only one sample to determine the whole set of materials properties for single domain PZN–6.5%PT single crystals by combining the ultrasonic pulse-echo (UPE) method and the resonance ultrasonic spectroscopy (RUS) for the elastic and piezoelectric coefficients and the impedance analyzer for dielectric measurements. Comparison with other reported results show the advantage of our methodology and such self-consistent date set would facilitate fundamental studies on domain engineering technique as well as device design optimization using finite element software.

Fabrication and characterization of aluminum - magnetic shape memory alloy composites

Smart composites, manufactured with embedded functional materials, hold the potential for a new type of structural health monitoring systems. The work herein focuses on how embedding Ni 43 Co 7 Mn 39 Sn 11 metamagnetic shape memory alloy (MMSMA) sensory particles into pure aluminum matrix modifies the chemical constitution and mechanical properties of both materials. Martensitically transforming particles in pure Al or Al alloys can interact with crack tip stress fields and undergo stress-induced martensitic transformation. This process emits acoustic signals and changes the magnetic state of the particles, which can then be exploited using acoustic monitors and/or magnetic sensors to determine the crack locations. Fabrication of these composites consisted of consolidation of homogeneously mixed powder precursors containing 10 vol% of Ni 43 Co 7 Mn 39 Sn 11 MMSMA particles. Elemental composition, hardness, and elastic modulus of the embedded particles and resulting diffusion region between the particles and the matrix were determined using wavelength dispersive spectrometry and instrumented nanoindentation. Elastic constants of the sintered bulk composites were also experimentally determined using resonant ultrasonic spectroscopy (RUS). Compositional analysis revealed that the diffusion region contained a diverse group of intermetallics. Nanoindentation results demonstrated that the diffusion region exhibits a high hardness value of 10.0 ± 0.3 GPa and an elastic modulus of 163 ± 5 GPa, as compared to the embedded particles having a hardness of 4.5 ± 0.4 GPa, and elastic modulus of 127 ± 6 GPa. Poisson's ratio and the stiffness tensor components (C 11 , C 12 , and C 44 ) were found to be 0.34, 214 GPa, 111 GPa, and 52 GPa, respectively, through RUS. The important material properties determined in the present study, especially the interface properties, can be used to model the composite system to optimize the particle size, distribution, and the size of the interfaces for desired bulk mechanical properties and damage sensing ability.

공진초음파분광법을 이용한 스퍼터링타겟 접합불량 검사 타당성 연구

스퍼터링타겟은 반도체 및 디스플레이 제조에 많이 활용되는 스퍼터링 공정의 원료와 전극역할을 하는 후면판을 접합시킨 것으로써, 타겟 재료와 후면판의 접합상태 불량은 제품의 품질이나 공정 효율에 많은 영향을 미치므로 엄격한 접합품질의 사전 검사가 요구된다. 기존 대부분의 스퍼터링타겟의 검사는 수침초음파스캔 방법을 이용하여 검사를 수행하였으나, 최근 디스플레이 공정에 많이 사용되는 재료중 물에 반응하는 IGZO(Indium Gallium Zinc Oxide)계열의 타겟의 경우 수침 검사가 어려워서 적절한 검사 수행의 어려움이 있었다. 본 연구에서는 전자기음향트랜스듀서(EMAT, electromagnetic acoustic transducer)와 초음파공진분광 기법을 이용하여 물과 접촉 없이 스퍼터링타겟의 접합불량을 검사하는 방법을 제안하고자한다. 이를 위해서 대상이 되는 스퍼터링타겟 시편의 검사에 적합한 EMAT을 제작하고 접합면의 공진분광 특성을 스캔하여 접합불량을 검사하였다. 측정결과 폭 1 mm 이상의 접합 손상부를 검출하였으며, 제안한 방법의 스퍼터링타겟 접합불량 검사 가능성을 확인하였다.

Non-negative differential evolution for particle sizing from ultrasonic attenuation spectroscopy

Ultrasonic attenuation spectroscopy (UAS) is a potentially characterising technique for nano-meter size materials. It is the inversion of the ultrasonic attenuation spectrum to particle size distribution (PSD) by using an optimisation technique. Because the particle size is non-negative number, the inversion has to be optimised in the non-negative real number domain. However, many optimisation techniques have traditionally added the non-negative constrain into a cost function as a result the function becoming complex. In this article, the modification of the differential evolution (DE) technique has been proposed to narrow the searching solution domain bounded in the non-negative real number domain. An absolute function has been added to a mutant vector of the DE technique to guarantee the solution is non-negative real number. This technique is called DE-Nonneg technique. The technique has been demonstrated by characterising size of silica suspension. The optimisation results show that the PSD predictions are comparatively to simulated annealing (SA) technique. Moreover, the performance of DE-Nonneg could be improved via adjusting the parameters (expanding factor, cross over, number of parameters and mutation type) following the guideline addressed here. In addition, it is also possible to predict the PSD without using the structural PSD model. With this advantage, DE-Nonneg could possibly be applied for other non-negative optimisation problems.

Acoustic probing of the particle concentration in turbulent granular suspensions in air

Dilute gas–particle suspensions in which the particles are carried by the fluid are found in various industrial and geophysical contexts. One fundamental issue that limits our understanding of such systems is the difficulty to obtain information on the particle concentration inside these often optically opaque suspensions. To overcome this difficulty, we develop ultrasonic spectroscopy to monitor the local particle concentration phi of glass particles (with diameters dsim 77 upmum or 155 upmum) suspended in air. First, we determine the minimal air velocity, U^*, necessary to suspend the particles from the maximum decrease in the transmitted wave amplitude and velocity of ultrasound propagating through the suspension. Next, setting the air velocity at U^*, we increase the mass of particles and monitor acoustically the local solid volume fraction, phi, by measuring the ultrasound wave attenuation coefficient and phase velocity as a function of frequency on the basis of classical scattering and hydrodynamic models. For the frequency ranges and suspensions considered here, the viscous dissipation dominates over scattering and thermal conduction losses. We show that, for a characteristic air velocity U^*, the locally measured phi reaches a critical value, in agreement with a recent study on turbulent gas–particle mixtures. Moreover, we find that this critical phi increases with the size of the particles. Finally, analysis of the temporal fluctuations of the locally measured solid volume fraction, suggests that high density regions (clusters) are present even in suspensions with concentrations below the critical concentration. This differs from the current hypothesis according to which the critical concentration coincides with the onset of cluster formation.

Advances in Analysis of Milk Proteases Activity at Surfaces and in a Volume by Acoustic Methods.

This review is focused on the application of surface and volume-sensitive acoustic methods for the detection of milk proteases such as trypsin and plasmin. While trypsin is an important protein of human milk, plasmin is a protease that plays an important role in the quality of bovine, sheep and goat milks. The increased activity of plasmin can cause an extensive cleavage of β-casein and, thus, affect the milk gelation and taste. The basic principles of surface-sensitive acoustic methods, as well as high-resolution ultrasonic spectroscopy (HR-US), are presented. The current state-of-the-art examples of the application of acoustic sensors for protease detection in real time are discussed. The application of the HR-US method for studying the kinetics of the enzyme reaction is demonstrated. The sensitivity of the acoustics biosensors and HR-US methods for protease detection are compared.

Thickness measurement via local ultrasonic resonance spectroscopy

Local ultrasonic resonance spectroscopy (LURS) is a new approach to material inspection, where the specimen is locally excited by a short mechanical impulse while its local mechanical response is recorded at a position nearby. The local material and geometrical properties can be extracted from the frequency spectrum of the response and visualized by performing a scan over the inspected area. In our experiment, the plate thickness and the reliefs of both plate surfaces (plate curvature) were obtained from thickness resonance and time of arrival analysis without physical contact to the specimen. Ultrasound was generated on the specimen surface by a laser pulse. Local mechanical response of a carbon fiber-reinforced polymer plate with a thickness ranging from 0.6 mm to 4.3 mm was recorded with a broadband optical microphone in through-transmission setup. The precision of this arrangement greatly exceeded the precision of conventional methods limited by the ultrasound wavelength. For thicknesses in the range around 1 mm, standard deviations of up to several µm were achieved. An influence of the through-plate ultrasound velocity on the measured relief of the plate surface nearest to the optical microphone was eliminated by a joint evaluation of thickness resonance and time of arrival. Furthermore, we demonstrated that internal delaminations have an influence on the spectrum of the local mechanical response and can therefore be detected by LURS.

Study of cholesterol’s effect on the properties of catanionic vesicular systems: Comparison of light-scattering results with ultrasonic and fluorescence spectroscopy

This work is focused on the study of properties associated with the effect of cholesterol levels on the stability of vesicular systems based on the ion pair amphiphile hexadecyltrimethylammonium-dodecylsulphate (HTMA-DS) at laboratory temperature. The HTMA-DS catanionic system was doped with dioctadecyldimethylammonium chloride in a 9:1 M ratio and cholesterol in the amount of 0, 3, 13, 23, 33, 43, 53, 63, and 73 mol.% was added. In this system, the size distributions were studied using the dynamic light-scattering technique and the zeta potential was determined. These standard techniques were supplemented by ultrasonic and fluorescence spectroscopy techniques. Due to low stability and high opalescence of samples, spectral techniques were used only for the samples with cholesterol content above 23 mol.%. The results from High-Resolution Ultrasonic Spectroscopy and from Fluorescence Spectroscopy are in agreement. They equally point to a change in the amount of hydration water in the membrane, the largest amount of which is present in the samples with 43 and 53 mol.% cholesterol. Using the light-scattering technique, the short-term stability of prepared vesicular systems was also observed over the first 36 days. Obtained results confirmed that the most stable systems are those containing 43 or 53 mol.% of cholesterol.

Proof of Concept for Pultrusion Control by Cure Monitoring Using Resonant Ultrasound Spectroscopy

The increasing demand for low cost consistent quality composite materials, especially of the automotive industry, creates the necessity for fast high quality processes. Pultrusion is one of the processes that can fulfill this demand. While the process is highly automated, manufacturing parameters still have to be chosen manually. The choice of line speed, mould temperature and injection pressure is based on best practice and therefore requires manual optimization that results in cost intensive manufacturing errors and suboptimal machine productivity. This paper presents a possible solution for this problem by providing an on-line cure monitoring approach that allows to overcome this challenge. Resonant Ultrasonic Spectroscopy (RUS) shows a high potential for in-line cure monitoring inside the pultrusion tool. RUS has been adapted for the first time in a pultrusion process. This paper focuses on the successful application of this technique to control the pultrusion process based on the state of cure of the material inside of the tool. As one of the only techniques for in-line cure monitoring which can be used continuously in closed tools despite high abrasion, it provides a new insight into the pultrusion process.

Application of high-resolution ultrasonic spectroscopy for real-time monitoring of trypsin activity in β-casein solution

High-resolution ultrasonic spectroscopy (HR-US) was applied for real-time monitoring of β-casein hydrolysis by trypsin at various conditions for the first time. The technique is based on the precision measurement of hydration changes proportional to the number of peptide bond hydrolyzed. As HR-US exhibits ultrasonic transparency for most solution, the analysis did not require optical transparency like for 2,4,6-trinitrobenzenesulfonic acid (TNBS) assay. Appropriate enzymatic models were fitted with degree of hydrolysis (dh) profiles to provide kinetic and mechanistic description of proteolysis in terms of initial hydrolysis rate, r0, and rate constant of hydrolysis, kh, and enzyme inactivation, kd. Maximal r0 and dh were obtained at 45 °C and pH 8. The exponential dependence of kinetic parameters allowed determination of the activation (EA = 50.3 ± 7 kJ/mol) and deactivation (ED = 62.23 ± 3 kJ/mol) energies of hydrolysis. The ultrasonic assay provided rapid detection of trypsin activity even at sub-nanomolar concentration.

Particulate Metal Composites as Backing for Ultrasonic Transducers for Continuous Nondestructive Measurements at Moderate and High Temperatures.

There is an increasing need for ultrasonic transducers able to operate continuously at high temperatures in many industrial sectors. Operating temperatures may be 600 °C and higher. There is not any commercial solution to deal with such applications, and only a few ultrasonic prototype probes exist. It is, therefore, important to find new materials suitable for the manufacture of high-temperature ultrasonic probes. One important element of ultrasonic probes is the backing as it enables the control of both sensitivity and bandwidth. The goal of this article is to explore the possibility of using particulate metal composite as a high-temperature backing elements. Several tin-tungsten composites with different tungsten volume fractions were produced by uniaxial pressing. The backings were characterized by ultrasonic spectroscopy. The backings have an impedance ranging from 25 to 31 MRayl with attenuation at least equal to 20 dB/cm and up to 191 dB/cm. In order to operate at 600 °C, a sample of Al/W composite was produced. Its impedance ranged from 8 to 10 MRayl with a mean attenuation of around 156 dB/cm at 4.5 MHz. The metallic composites, therefore, have ultrasonic properties suitable for use as backing. Moreover, they are relatively easy to manufacture. These are, therefore, very interesting materials for high-temperature ultrasonic probe applications.

Application of acoustic models for polydisperse emulsion characterization using ultrasonic spectroscopy in the long wavelength regime

Ultrasonic spectroscopy is a technique that often has been used for measuring the particle size distribution in suspensions and emulsions. The ability to analyze concentrated heterogeneous systems and optically opaque samples, without the need for dilution, is the major advantage over alternative technologies, such as light scattering method. Several physical models used to interpret the measured attenuation spectra have been applied considering monodisperse particles. However, the polydisperse particle distributions are found in many practical applications, for example, in crude oil emulsions during droplet coalescence or flocculation. The polydispersity effects are usually important and need to be incorporated into theoretical predictions. For this work, acoustic spectroscopy within the frequency range 6–14 MHz was used to measure the droplet size distribution of water-in-sunflower oil emulsions for a volume fraction range from 10 to 50 % and considering monomodal size distribution. The results obtained from experimental attenuation spectra have been compared with the predictions of acoustic models from simple and multiple scattering, extended multiple scattering, and other simpler models of propagation usually applied to the long wavelength regime. The droplet size distributions from theoretical and experimental attenuation spectra were calculated with a deconvolution algorithm. The size distribution results obtained by ultrasonic spectroscopy showed good agreement with those obtained by laser diffraction analysis. The findings indicate that the methodology employed in this study is suitable for polydisperse particle size characterization for moderate concentrations up to 20 %.

Surface Density of the Spongy and Palisade Parenchyma Layers of Leaves Extracted From Wideband Ultrasonic Resonance Spectra.

The wide band and air-coupled ultrasonic resonant spectroscopy together with a modified Simulated Annealing metaheuristic algorithm and a 1D layered acoustic-model are used to resolve the structure of plant leaves. In particular, this paper focuses on the extraction of the surface density of the different layers of tissue in leaves having a relatively simple structure. There are three main reasons to select the surface density as the focus of this study: (i) it is a parameter directly extracted by the proposed technique and it requires no further processing, (ii) it is relevant in order to study the dynamic of the water within the different tissues of the leaves and also to study the differential development of the different tissues, and (iii) unlike other parameters provided by this technique (like resonant frequency, impedance, ultrasonic elastic modulus, or ultrasonic damping), this parameter can be easier to understand as it is a direct measure of mass per unit surface. The selection of leaves with a simple structure is justified by the convenience of avoiding an unnecessary complication of the data extraction step. In this work, the technique was applied to determine the surface density of the palisade and spongy parenchyma layers of tissue of Ligustrum lucidum, Vitis vinifera, and Viburnum tinus leaves. The first species was used to study the variation of the surface density at full turgor with the thickness of the leaf, while the two other species were used to study the variation of the surface densities with the variation in the leaf relative water content. Consistency of the results with other conventional measurements (like overall surface density, and cross-section optical and cryo-SEM images) is discussed. The results obtained reveal the potential of this technique; moreover, the technique presents the additional advantage that can be applied in-vivo as it is completely non-invasive, non-destructive, fast, and equipment required is portable.

Numerical and Experimental Characterization of Elastic Properties of a Novel, Highly Homogeneous Interpenetrating Metal Ceramic Composite

An interpenetrating aluminum–alumina composite is presented, based on a ceramic foam manufactured via a novel slurry‐based route resulting in a highly homogeneous preform microstructure in contrast to other preform techniques. The metal matrix composite (MMC) is produced by infiltrating the open‐porous ceramic preform with molten aluminum at 700 °C using a Argon‐driven gas pressure infiltration process. The resulting MMC and the primary ceramic foam are investigated both numerically and experimentally in terms of microstructural characteristics. In addition, the mechanical behavior of the material as well as the structural and material interactions on the microscale are investigated. To characterize the MMC regarding mechanical isotropy, elastic properties are determined experimentally via ultrasonic phase spectroscopy (UPS). A fast Fourier transform (FFT) formulation is used to simulate the complex 3D microstructure with reasonable effort based on image‐data gathered from high‐resolution X‐ray computed tomography (CT) scans of the ceramic foam as computational grid. Simulations prove that the material properties are, indeed, considered as highly homogeneous with respect to the material microstructure. A comparison with effective experimental investigations confirms these findings.

Exploring conformational change profile of n-propyl ester of formic acid by combining ultrasonic relaxation spectroscopy and molecular orbital calculations

We report a detailed investigation of the ultrasonic absorption spectra of n-propyl formate in the liquid state over a wide frequency and temperature range under constant pressure. The ultrasonic absorption measurements were performed by standard acoustic resonator and pulse techniques. A single relaxational phenomenon has been observed and is attributed to a unimolecular reaction due to a conformational change of the n-propyl formate molecule in the liquid state. The characteristic relaxation frequency increases with increasing temperature and vise versa. In an effort to confirm the assignment of the relaxation process and to determine the corresponding thermodynamic properties, relaxation parameters were further investigated as a function of temperature. Activation enthalpy and enthalpy difference between the two isomeric forms have been estimated equal to ΔH∗ = 4.21 ± 0.16 kcal/mol and ΔH0 = 6.21 ± 0.29 kcal/mol, respectively. The corresponding energy barrier was estimated equal to ΔEexperimental = 10.42 ± 0.33 kcal/mol. Molecular orbital calculations have been applied to obtain the standard enthalpy of formation for n-propyl formate at various dihedral angles around C–O bond. The results exhibited two clear minimum standard enthalpies of formation and the energy barrier has been calculated equal to ΔΕ = 11.62 kcal/mol, close to the experimental value considering that the calculation was performed in a vacuum environment. The results confirm the absence of shear viscosity relaxation in this frequency range. The ratio of the volume viscosity to the static shear viscosity ηV/ηS has been determined revealing a clear temperature dependent and ηV>ηS supporting the assignment of the observed relaxation process to the rotational equilibrium. The results are analyzed in view of the current phenomenological status of the field.

Osmolality and molar mass of oligosaccharides in breast milks and infant formula during hydrolysis of lactose. Application of high-resolution ultrasonic spectroscopy

β-Galactosidase formulations can be added to infant milks prior to feeding to reduce the level of lactose and to avoid symptoms of lactose intolerance. The hydrolysis of lactose affects osmolality, which is an important property of infant milk. This paper introduces novel ultrasonic technology for precision, real-time, non-destructive monitoring of osmolality of infant milks, including breast milk, during enzymatic hydrolysis of lactose by supplemental β-galactosidases. This technology can be utilised in the development and testing of β-galactosidase formulations. Additionally, ultrasonic real-time measurements of the average degree of polymerisation and molar mass of milk saccharides throughout the hydrolysis are discussed. Comparison of the ultrasonic results with discontinuous data of osmometry and HPLC showed an excellent agreement between the different techniques. The results elucidate the osmolality dynamics involved in the enzymatic hydrolysis of lactose in milks.