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The problems and possibilities of passive thermoacoustical tomography are discussed. Algorithms for reconstruction of internal temperature in the human body are proposed. These algorithms take into account heat transfer and blood circulation and the absorption factor, obtained previously. The results of reconstruction of deep temperature in the human hand in simulations with the medium with a heated object are reported. These results support the possibility of the correlation measurements of the thermal acoustic radiation. Such measurements allow the information on ultrasound absorption by the object under study to be obtained and open the way to the development of a passive acoustic tomography system using a priori information on the absorption factor.

The propagation velocity and the absorption coefficient of ultrasound in a frequency range of 5–2800 MHz in a n-pentanol–nitromethane solution in a vicinity of its critical stratification point from the homogeneous state side have been studied. The research make it possible to reveal the influence of concentration fluctuations on the sound propagation velocity. Three regions of dynamical parameters are analyzed: the mean-field (wтFL ≪ 1), fluctuation (wтFL ≫ 1), and transition (crossover, wтFL = 1) ones. On the basis of experimental data, the temperature dependence of the concentration fluctuation relaxation time т(T) is studied, and its magnitude т0 is determined. The contribution to the fluctuation part of the sound absorption coefficient at high frequencies (w > 300 MHz), which is connected with the sound scattering by concentration fluctuations near the critical stratification point is estimated., Проведенi дослiдження швидкостi поширення та коефiцiєнта поглинання звуку в розчинi н-пентанол-нiтрометан в iнтервалi частот 5–2800 МГц при пiдходi до його критичної точки розшарування з боку гомогенного стану дозволили визначити вплив флуктуацiй концентрацiї на акустичнi параметри. В термiнах динамiчних параметрiв дослiджено три областi: середнього поля wтFL ≪ 1, флуктуацiйна wтFL ≫ 1, та перехiдна – кросоверна wтFL = 1. На основi експериментальних даних в роботi дослiджено температурну залежнiсть часу релаксацiї флуктуацiй концентрацiї т(T), визначено його амплiтудне значення т0. На високих частотах (w > 300 МГц) оцiнено внесок у флуктуацiйну частину коефiцiєнта поглинання звуку, який пов’язаний iз розсiянням звуку на флуктуацiях концентрацiй поблизу критичної точки розшарування.

The equation of coefficient of ultrasound absorption is substantiated in terms of classical and quantum theories. Polytherms for liquid gold, scandium, chromium, and rhenium in a wide temperature range have been obtained for the first time.

International audience; A complete review of the literature data on the speed of sound and ultrasound absorption in pure ionic liquids (ILs) is presented. Apart of the analysis of data published to date, the significance of the speed of sound in ILs is regarded. An analysis of experimental methods described in the literature to determine the speed of sound in ILs as a function of temperature and pressure is reported, and the relevance of ultrasound absorption in acoustic investigations is discussed. Careful attention was paid to highlight possible artifacts, and side phenomena related to the absorption and relaxation present in such measurements. Then, an overview of existing data is depicted to describe the temperature and pressure dependences on the speed of sound in ILs, as well as the impact of impurities in ILs on this property. A relation between ions structure and speeds of sound is presented by highlighting existing correlation and evaluative methods described in the literature. Importantly, a critical analysis of speeds of sound in ILs vs those in classical molecular solvents is presented to compare these two classes of compounds. The last part presents the importance of acoustic investigations for chemical engineering design and possible industrial applications of ILs.

The Stokes-Kirchhoff theory is used to study the ultrasound absorption coefficient in 33 liquid metals (25 metals are analyzed for the first time) at the melting temperature. A relation between the absorption coefficient and the conduction electron concentration is found. The ratio of the absorption coefficient caused by heat conduction to the absorption coefficient caused by viscosity is estimated.

The temperature dependence of the ultrasound wave absorption in bulk p-Cd0.2Hg0.8Te crystals free from low-angle grain boundaries has been studied experimentally for the first time in the frequency range 10–55 MHz and the temperature interval 150–300 K, and the corresponding results of measurements are presented. The maximum value of absorption coefficient is found to increase and to shift toward higher temperatures, as the ultrasound frequency grows. The results obtained can be satisfactorily explained in the framework of the Brailsford model, which associates the ultrasound absorption with vibrations of thermally activated dislocation kinks. The characteristic parameters of this model for p-Cd0.2Hg0.8Te are determined; namely, the frequency coefficient fk≈ 6×10^9 Hz and the kink diffusion activation energy Wk≈ 0.11 eV. The dislocation concentration is also evaluated (a ≈ 2×10^10 m^−2), with the determined value being consistent with that obtained by the selective etching method (0.7×10^10 m^−2)., Вперше наведено результати експериментального дослiдження температурної (150–300 K) залежностi поглинання ультразвукових (УЗ) хвиль у об’ємних кристалах p-Cd0,2Hg0,8Te, якi не мiстять малокутових границь, у частотному дiапазонi 10–55 МГц. Виявлено, що при збiльшеннi частоти УЗ спостерiгається збiльшення максимального значення коефiцiєнта поглинання та його зсув у бiк високих температур. Показано, що експериментальнi результати задовiльно пояснюються в рамках моделi Брейсфолда, яка розглядає поглинання УЗ хвилi за рахунок коливання термоактивованих дислокацiйних перегинiв. Визначено характернi параметри даної моделi для p-Cd0,2Hg0,8Te, а саме частотний фактор (6 · 10^9 Гц) та активацiйна енергiя руху перегинiв (0,11 еВ), а також проведено оцiнку густини дислокацiй (2 · 10^10 м^−2), яка узгоджується з даними, отриманими методом селективного травлення (0,7·10^10 м^−2).

The soft tissue thermal index defined in the Output Display Standard is not applicable to eye exposures because of unique eye properties such as high ultrasound absorption in the lens and orbital fat. To address this potential safety issue, the U.S. Food and Drug Administration has recommended a maximum exposure level for ophthalmic exams of 50 mW/cm2 (derated spatial-peak temporal-average intensity, ISPTA.3) based on a model of ultrasound propagation in the eye. To gain a better understanding of actual temperature rise as a function of ISPTA.3, an ex vivo experimental study within the porcine lens was performed. Both temperature and acoustic pressure were measured simultaneously in the lens using a fiberoptic probe. At ISPTA.3 = 50 mW/cm2, the maximum and average temperature rises over 133 measurements were 0.23°C and 0.09°C, respectively. A 1.5°C temperature rise was not obtained until ISPTA.3 ≈ 435 mW/cm2. The data indicate that operating below the Food and Drug Administration guidance level should result in relatively low heating in ophthalmic exposures.

Experimental results on the use of the ultrasound phase conjugation (PC) for measuring the coefficient of sound absorption in test objects simulating an inhomogeneous medium are reported. The objects were made of gelatin with local inclusions in the form of air bubbles. The results obtained at 5 MHz by the conventional insert/substitution method were compared with measurements by the modification of the method that employs PC of ultrasound. It is shown that the PC compensation for the distortions of the probing ultrasound beam in an inhomogeneous medium leads to a decrease in the measured ultrasound attenuation and thus allows a more accurate description of the sound absorption coefficient than the conventional method without compensation.

Purpose: Endocavitary high intensity contact ultrasound (HICU) may offer interesting therapeutic potential for fighting localized cancer in esophageal or rectal wall. On-line MR guidance of the thermotherapy permits both excellent targeting of the pathological volume and accurate preoperatory monitoring of the temperature elevation. In this article, the authors address the issue of the automatic temperature control for endocavitary phased-array HICU and propose a tailor-made thermal model for this specific application. The convergence and stability of the feedback loop were investigated against tuning errors in the controller’s parameters and against input noise, throughex vivo experimental studies and through numerical simulations in which nonlinear response of tissue was considered as expected in vivo. Methods: An MR-compatible, 64-element, cooled-tip, endorectal cylindrical phased-array applicator of contact ultrasound was integrated with fast MR thermometry to provide automatic feedback control of the temperature evolution. An appropriate phase law was applied per set of eight adjacent transducers to generate a quasiplanar wave, or a slightly convergent one (over the circular dimension). A 2D physical model, compatible with on-line numerical implementation, took into account (1) the ultrasound-mediated energy deposition, (2) the heat diffusion in tissue, and (3) the heat sink effect in the tissue adjacent to the tip-cooling balloon. This linear model was coupled to a PID compensation algorithm to obtain a multi-input single-output static-tuning temperature controller. Either the temperature at one static point in space (situated on the symmetry axis of the beam) or the maximum temperature in a user-defined ROI was tracked according to a predefined target curve. The convergence domain in the space of controller’s parameters was experimentally exploredex vivo. The behavior of the static-tuning PID controller was numerically simulated based on a discrete-time iterative solution of the bioheat transfer equation in 3D and considering temperature-dependent ultrasound absorption and blood perfusion. Results: The intrinsic accuracy of the implemented controller was approximately 1% inex vivo trials when providing correct estimates for energy deposition and heat diffusivity. Moreover, the feedback loop demonstrated excellent convergence and stability over a wide range of the controller’s parameters, deliberately set to erroneous values. In the extreme case of strong underestimation of the ultrasound energy deposition in tissue, the temperature tracking curve alone, at the initial stage of the MR-controlled HICU treatment, was not a sufficient indicator for a globally stable behavior of the feedback loop. Our simulations predicted that the controller would be able to compensate for tissue perfusion and for temperature-dependent ultrasound absorption, although these effects were not included in the controller’s equation. The explicit pattern of acoustic field was not required as input information for the controller, avoiding time-consuming numerical operations. Conclusions: The study demonstrated the potential advantages of PID-based automatic temperature control adapted to phased-array MR-guided HICU therapy. Further studies will address the integration of this ultrasound device with a miniature RF coil for high resolution MRI and, subsequently, the experimental behavior of the controllerin vivo.

We have measured the ultrasound velocity and absorption in BeO, Al2O3, ZrO2, and SiO2 ceramics. The results indicate that the ultrasound velocity in oxide ceramics depends on the nature of the basic oxide component, the density of the material, and the preferential alignment of the grains. The ultrasound velocity in ceramics is shown to correlate with their thermal conductivity: with increasing thermal conductivity, the ultrasound velocity increases. The ultrasound absorption in oxide ceramics decreases with decreasing temperature, and vice versa, with increasing temperature, the ultrasound attenuation coefficient increases.

Recently, ultrasonic surgical knives have been applied in a variety of surgical operations. In this paper, the operation frequency of a surgical knife is focused on. Prototype ultrasonic knives operated at 24.3, 44.3, and 71.9 kHz were constructed. Differences in the effects on soft tissue depending on the operation frequency were investigated using these knives. Frequency characteristics were measured using two parameters: coagulation ratio and coagulated depth. For the same vibration velocity, at a lower frequency, the distribution of the coagulated tissue was deep and in a narrower region around the center of the tip. For the same vibration amplitude, the coagulated depth at each frequency was similar for all these frequencies. Furthermore, the dependences of tissue coagulation on the vibration velocity, pressure load, contact of the tip with tissue, and direction of vibration were investigated. From these investigations, it was found that the mechanical effect, rather than ultrasound absorption, is the dominant factor in tissue coagulation.

We examine the Ehrenfest relations for the elastic constants of the spin-triplet superconducting state in Sr 2 RuO 4 . It is shown on a phenomenological level that the relations for different sound modes are not independent. This result may be used to analyze experimental data of sound velocity renormalization in the superconducting state. Finally, the relation between couplings of the order parameter and uniaxial strain is discussed from a microscopic point of view for the particular band structure of Sr 2 RuO 4 .

AIM Diagnostic ultrasound is a powerful, versatile and safe investigation tool in modern medicine. Methods are described, and conclusions are drawn and recommendations given for a responsible use of diagnostic ultrasound. METHOD AND RESULTS Because of the increasing ultrasonic power penetrating the body, diagnostic techniques cannot always be applied without risk. The increase in temperature induced by ultrasound absorption should be considered a potential hazard in certain applications. The paper presents the physical basis for a quantitative estimation of the risk of a specific treatment plan. Mathematical models and the thermal index are described. CONCLUSION Our findings and recommendations form a viable basis for the responsible use of diagnostic ultrasound.

The aim of our study was to investigate the association between nutrient factors and the osteo-sono assessment index (OSI) for calcaneus of young Japanese women. The subjects consisted of 965 young women aged from 18 to 22 years studying at the Department of Food and Nutrition at Nakamura-Gakuen University. The OSI was measured by ultrasonic bone absorptiometry. We found that age, weight, height, exercise, as well as the daily intakes of calcium, phosphorus, protein, energy and sodium were the main factors related to OSI in young women. Positive associations were observed between the OSI and the weight, exercise and daily intakes of calcium, protein and energy, whereas while negative associations were seen between the OSI and the age, height and daily intakes of phosphorus and sodium. In addition, all of these factors were also independently related to the OSI.

Ultrasound absorption technique was applied to study the effect of 8-methoxypsoralen (8-MOP), quercetin, and umbeliferone on the organization of dipalmitoylphasphatidylcholine (DPPC) membranes. Based on measurements of the ultrasound absorption coefficient in the region of phase transition temperature, it was stated that all the examined substances decrease the phase transition temperature of DPPC: quercetin - distinctly, 8-MOP and umbeliferone - not much. 8-MOP increases cooperativity of transition and the action of umbeliferone and quercetin depends on their concentrations. Different actions of these three examined compounds are associated with some differences in their structures.

Very narrow size distribution oil-in-water emulsions have been prepared by using a recently proposed selective creaming method. The emulsions have been characterized by static and dynamic light scattering measurements. The ultrasonic absorption of the emulsions has been measured with an acoustic interferometer at frequencies between 0.5 and 10 MHz for a wide range of concentrations and droplets sizes. The comparison of the experimental results with existing theories shows an excellent agreement at oil volume fractions up to 0.15. The discrepancy between theory and experiments observed at higher volume fractions is attributed to thermal interactions between droplets for which a semi-quantitative model is proposed. Rdsumd. Des 6mulsions d'huile dans l'eau pr6sentant une distribution en taille trbs 6troite ont 6t6 pr6par6es gr£ce h une m6thode r6cemment propos6e, fondle sur le cr6mage s61ectif des gouttelettes. Ces 6mulsions ont 6t6 caract6ris6es par diffusion statique et dynamique de la lumibre. L'abiorption ultrasonore des 6mulsions a 6t6 mesur6e h l'aide d'un interf6rombtre acous- tique h des fr6quences comprises entre 0,5 et 10 MHz pour une large gamme de concentrations et de dimensions des gouttelettes. L'accord des rdsultats expdrimentaux avec les thdories existantes est excellent pour les fractions volumiques en huile infdrieures h IS ~. L'dcart entre thdorie et expdrience qui apparait aux fractions volumiques plus dlevdes est attribud aux interactions thermiques entre gouttelettes, pour lesquelles un modAle semi-quantitatif est proposd.

A new expression of the backscattering form function |f∞(k0a,θ)| for cylindrical targets, suspended in an inviscid fluid in a plane incident sound field, is presented. The theory is modified to include the effects of absorption of shear and compressional waves in viscoelastic materials. The numerical results presented show how damping effect due to ultrasound absorption influences the cylinder’s material properties.

Floyd Dunn greatly contributed to the history of biomedical ultrasound microscope (USM) in Japan. Ten years after the concept of ultrasound microscope was proposed by Sokolov of Soviet Union, he realized the ultrasound absorption microscope in 1959. During the time he directed the Bioacoustics Research Laboratory at the University of Illinois, many Japanese researches stayed in his laboratory. Especially, the researchers from Tohoku University learned both technology and philosophy of USM and they started development of scanning acoustic microscopy for medicine and biology in 1982. The USM system had been used for nearly 30 years until the Great East Japan Earthquake destroyed the system. Not only USM, other high frequency ultrasound imaging was also developed in 1990s. Especially, clinical application of intravascular ultrasound filled a gap between several MHz ultrasound used in conventional B-mode and 100 MHz used in USM. High frequency technology and computer science helped developing new generation U...

The author describes the inspiration for the experiment by Hebel and Slichter to measure the nuclear spin–lattice relaxation time in superconductors, the design considerations for the experiment, the surprising experimental results, their theoretical treatment using the Bardeen–Cooper–Schrieffer theory, and how comparing the nuclear relaxation results with those for ultrasound absorption confirmed the central idea of the BCS theory, the BCS pair wave function.

Microbubbles were isolated by size using differential centrifugation, and the effect of microbubble size on the acoustics and kinetics of contrast ultrasound imaging was measured in the mouse kidney. Microbubbles in the 1–2 µm diameter size range comprise over 90% of the microbubbles in freshly generated and commercially available lipid-coated microbubbles. These smaller microbubbles attenuated strongly without producing much backscatter, thus behaving like a negative contrast agent. The high degree of ultrasound absorption may be due to strong damping by the shell. On the other hand, microbubbles in the 4–5 and 6–8 µm diameter size ranges were highly echogenic. Also, larger microbubbles exhibited longer contrast persistence, indicating that dissolution is the main mechanism of elimination. For example, 6–8 µm diameter microbubbles circulated for greater than 15 minutes at a dose of 5×10^8 microbubbles/mL in a 0.1-mL bolus. These results demonstrate that the magnitude and duration of contrast enhancement is strongly dependent on the microbubble size distribution.

Despite the increasing adoption of other imaging modalities, ultrasound guidance is widely used for surgical procedures and clinical imaging due to its low cost, non-invasiveness, and real-time visual feedback. Many ultrasound-guided procedures require extensive training and where possible training on simulations should be preferred over patients. Computational resources for existing approaches to ultrasound simulation are usually limited by real-time requirements. Unlike previous approaches we simulate freehand ultrasound images from CT data on the Graphics Processing Unit (GPU). We build upon the method proposed by Wein et al. for estimating ultrasound reflection properties of tissue and modify it to a computationally more efficient form. In addition to previous approaches, we also estimate ultrasound absorption properties from CT data. Using NVIDIA's "Compute Unified Device Architecture" (CUDA), we provide a physically plausible simulation of ultrasound reflection, shadowing artifacts, speckle noise and radial blurring. The same algorithm can be used for simulating either linear or radial imaging, and all parameters of the simulated probe are interactively configurable at runtime, including ultrasound frequency and intensity as well as field geometry. With current hardware we are able to achieve an image width of up to 1023 pixels from raw CT data in real-time, without any pre-processing and without any loss of information from the CT image other than from interpolation of the input data. Visual comparison to real ultrasound images indicates satisfactory results.

In polycrystalline specimens of intermetallic SmFe2 the temperature dependences are measured of the sound velocity and of the sound absorption coefficients. By contrast with earlier investigations, anomalies are detected in the acoustic properties at two spin-reorientation temperatures rather than at one. The temperature dependences are characterized by a hysteresis. Possible causes of the observed anomalies in the acoustic properties of SmFe2 are discussed. In polykristallinen Proben von intermetallischem SmFe2 werden die Temperaturabhangigkeiten der Schallgeschwindigkeit und der Schallabsorptionskoeffizienten gemessen. Im Gegensatz zu fruheren Untersuchungen werden Anomalien in den akustischen Eigenschaften bei zwei Spin-Reorientie-rungstemperaturen statt bei einer gefunden. Die Temperaturabhangigkeiten sind durch eine Hysterese charakterisiert. Mogliche Grunde fur die beobachteten Anomalien in den akustischen Eigenschaften des SmFe2 werden diskutiert.

The diagnostic information provided by ultrasound methods is determined to a significant extent by the state of research in ultrasound absorption, scattering, and propagation velocity in different biological mediums. On the strength of their complexity, these problems are far from being adequately understood at the present time. Thus, any satisfactory explanation for the observed sound attenuation dependencies on both physical parameters (wave frequency, temperature) and properties of the tissue itself [2] is lacking. Constructing models of the physical interaction of ultrasound with biological tissues is the present task. In spite of the fact that a lot of experimental data has been gathered, the diffi

Resume Des mesures de vitesse et d'attenuation d'ondes ultrasonores longitudinales et transversales ont ete effectuees sur des melanges de polystyrene et de polyethylene dans l'intervalle de temperatures (− 70°C, + 20°C). Les modules mecaniques complexes ont ete determines et leurs variations suivies en fonction de la composition des melanges. Enfin, une relation entre vitesse et attenuation a ete etudiee sur ces melanges.

In most cases ultrasound is generated by piezoelectric transducers. The principle can be easily seen by a one-dimensional consideration.

The problems and possibilities of passive thermoacoustical tomography are discussed. Algorithms for reconstruction of internal temperature in the human body are proposed. These algorithms take into account heat transfer and blood circulation and the absorption factor, obtained previously. The results of reconstruction of deep temperature in the human hand in simulations with the medium with a heated object are reported. These results support the possibility of the correlation measurements of the thermal acoustic radiation. Such measurements allow the information on ultrasound absorption by the object under study to be obtained and open the way to the development of a passive acoustic tomography system using a priori information on the absorption factor.

The vast majority of the physical chemical data available for nicotine is very old. In virtually every instance, there is a serious need for update using contemporary techniques. The vapor pressure of neat nicotine appears to be the only exception. A number of thermodynamic parameters were calculated from available data for aqueous nicotine. Calorimetric data regarding heat and heat capacities of solution are essential to a thermodynamic understanding of aqueous nicotine. Instrumental techniques such as light scattering, ultrasound absorption, dielectric relaxation and NMR, which have proven highly informative regarding other amphiphilic molecules, are yet to be applied to the nicotine–water system. The amphiphilic nature of nicotine is of interest not only from a physical chemical point of view, but potentially has implications for biological systems as well. It is well known that amphiphilic alcohols can have strong hydrophobic interactions with proteins.

The principal properties involved in ultrasonic tissue characterization are the speed with which the wave propagates and the absorption of the wave energy. Absorption is a material parameter, as it does not include the scattering and reflection properties included in the attenuation parameter. It is important that we obtain ever more absorption data of bio-materials in order to have a complete understanding of the interaction of ultrasound and living materials. Many studies of the ultrasonic analysis of tissues have been reported [1]-[11]. Here, analysis means that we have a material of unknown properties, and we wish to determine its characteristics. In the field of electrical engineering, for example, we also consider studies of “synthesis” of materials. First, analysis studies may be conducted, which lead to synthesis studies. The continuation of the processes leads to a deeper understanding of the media structure and to superior models. Thus, we think in terms of the synthesis of a model which has properties similar to that of human tissues, from which it may be expected that research on the origin of ultrasound absorption will be improved.

The author describes the inspiration for the experiment by Hebel and Slichter to measure the nuclear spin–lattice relaxation time in superconductors, the design considerations for the experiment, the surprising experimental results, their theoretical treatment using the Bardeen–Cooper–Schrieffer theory, and how comparing the nuclear relaxation results with those for ultrasound absorption confirmed the central idea of the BCS theory, the BCS pair wave function.

Photoacoustically generated air-ultrasonic pulses were used to determine the ultrasound absorption profiles of aerogel-glass interfaces. The results show the expected lack of homogeneity of such interfaces.

The variable distance pulsed phase-locked method is applied to study the temperature and frequency dependences of the rate and coefficient of ultrasound absorption in diethyl siloxane and ethyloctyl siloxane in the frequency range 4–63 MHz at temperatures from 293 to 348 K. Based on experimental data, the frequency dependence of the volume and shear viscosities is derived. The values of the shear and volume viscosity coefficients, as well as the relaxation times of processes discovered, are found.

The low temperature attenuation of acoustic surface waves has been measured in quench condensed AuxSn1−x films at a frequency of 300 MHz. Influence of the conduction electrons is clearly observed in the vicinity of the superconducting transition temperature. Our results give strong evidence for the presence of tunneling systems known from conventional glasses. The acoustic behaviour of our films can be interpreted in the framework of the tunneling model taking into account a restricted distribution of tunneling states and their interaction with conduction electrons.

Ultraschallabsorptionsuntersuchungen wurden an linearem und sternformigem Poly(propylenglykol) in einem Frequenzbereich von 0,1 bis 100 MHz durchgefuhrt. Beide Proben zeigen qualitativ das gleiche Relaxationsverhalten. Die Unterschiede in der Absolutgrose der Absorption konnen durch die Unterschiede der Molekulmasse beider Proben erklart werden. Ein zusatzlicher Absorptionsmechanismus durch die Sternstruktur wurde nicht nachgewiesen. Ultrasonic attenuation was measured with linear and star-shaped poly(propylene glycoles) in a frequency range from 0.1 to 100 MHz. Both samples exhibit the same relaxational behaviour qualitatively. The differences of the absorption values can be explained by differences of molecular mass. An additional contribution assigned to the star structure was not detected.

Absorption of ultrasonic waves has been investigated in the mixture of acetic acid and tetrachloromethane covering the complete concentration range. Measurements have been carried out at 20, 30 and 40°C within a frequency range from 3 to 57 MHz for strongly absorbing mixtures (rich in acetic acid) and 5–57 MHz for mixtures with lower absorption. At about 0.01 mole fraction of acetic acid a relaxation has been observed with a relaxation frequency of 20 MHz increasing rapidly with increasing concentration, so that its observation has become impossible at mole fractions of acid bigger than 0.07. At higher acid concentrations the well known low frequency relaxation has been observed. The relaxations are discussed in terms of coupled dimerization and cyclization reaction of acetic acid including the nonideality of the mixture. In this model the faster relaxation seems to be caused by the dimerization reaction.

The results of an ultrasonic study of a smectic C phase in a rotating magnetic field are presented. The observed dependence of the ultrasound absorption coefficient, α, as a function of the angle, φB, of rotation of the magnetic field is discussed. It is shown that the temperature variation of the parameters, determining the dependence α(φB) can be explained within the framework of a simple model of the smectic C phase.

Using an apparatus described in preceding papers, the speeds of sound in liquid acetonitrile were measured at temperatures from 240 to 475 K and pressures from the coexistence line up to 60 MPa. The inaccuracy is less than 0.17 per cent. These measurements were used to establish two equations; one for the speed of sound over the whole range as a function of temperature and pressure, and a second along the coexistence line as a function of temperature only.

Estimation des parametres de la fonction spectrale de relaxation du melange binaire de composition critique egale a 0,392, a differentes temperatures pres de la temperature critique egale a 26.42 o C

Sound velocities for binary mixtures of tetrachloroethylene with 1-propanol, 1-butanol. 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol were determined at 303.15 K. The results were analysed in terms of the free length theory (FLT) due to Jacobson and Collision factor theory (CFT) due to Schaaffs. The analyses showed that both theories predict satisfactorily sound velocities of the mixtures. Further, isentropic compressibility's, ks . of the mixtures were computed by combining sound velocities and density data derived from excess volumes. The deviation in isentropic compressibility, As, is negative over the whole range of composition for all the mixtures formed by tetrachloroethylene with alcohols. An inversion in the sign of Ks is observed certain ranges of concentration of tetrachloroethylene with 1-octanol. The deviation in isentropic compressibility was found to decrease with increase in chain length of the alcohol.

A single pulse time-domain technique is described for determining, via Fourier transform methods, the compressional wave ultrasound absorption coefficient in liquids contained in spherical reverberators over a frequency range from ≈ 200 kHz to 1 MHz. Only modest data storage and computational facilities are required. Such a technique offers an advantage over variable continuous frequency methods in that data for a given frequency range can be acquired ‘instantaneously’ and thus it is possible to monitor ultrasound absorption in time-varying systems. The method is illustrated by provision of absorption data in the frequency range 200 kHz–1 MHz for out-gassed water, aqueous solutions of the electrolyte cobaltous sulphate, with and without gas bubbles, and for the protein bovine serum albumin under conditions of acid pH obtained using spherical reverberators of 100 and 250 ml capacity.

On presente une nouvelle methode rapide, avec multiplexage de frequences, entierement optique de spectrometrie d'absorption d'ultrasons en phase gazeuse. Un laser a impulsions produit une impulsion acoustique de courte duree dans l'echantillon de gaz et les profils des impulsions acoustiques a 2 distances sont controles par des faisceaux sonde continus focalises

The amplitude dependence of ultrasound absorption due to dislocations, α, has been studied for single crystals of pure lead and indium as well as for lead doped with Tl, Sn or Bi, both in the superconducting and normal state and for a wide range of ultrasound amplitudes, e0. Pure and Tl-doped superconducting lead at large e0 displayed a maximum on the α(e0) dependence which became a plateau upon transition to the n-state. This is direct evidence for a change from static to dynamic dislocation hysteresis as a result of the increase in the electron drag constant. Limit values for the dislocation loop lengths have been estimated, viz. 2.4 × 10−4 cm < LN < 10.4 × 10−4 cm. In other single crystals the dynamic hysteresis occurred both in the n- and s-state. In all the single crystals, α increased with the increase of e0 above the maximum amplitude and onset of the plateau which was observed in both states. The effect is associated with non-linear phenomena arising at significant loop flexures. The amplitude dependence of the losses due to this effect has been analysed, the results of the analysis being in good agreement with the experimental data. An reinem Blei bzw. Indium sowie an mit Tl, Sn oder Bi dotiertem Blei wurde die versetzungsbedingte Amplitudenabhangigkeit der Ultraschallabsorption α in einem weiten Bereich der Ultraschallamplituden e0 sowohl im supraleitenden als auch im normalleitenden Zustand untersucht. Reines und Tl-dotiertes supraleitendes Blei entwickelt bei grosem e0 in der α(e0)-Abhangigkeit ein Maximum, welches zu einem Plateau beim Ubergang zum normalleitenden zustand wird. Dies ist ein direkter Beweis fur einen Wechsel von der statischen zur dynamischen Hysterese als Resultat der Zunahme der Konstanten der Elektronenreibung. Grenzwerte der Langen der Versetzungsschleifen wurden zu 2,4 · 10−4 cm < LN < 10,4 · 10−4 cm abgeschatzt. In anderen Einkristallen erscheint die dynamische Hysterese sowohl im n- wie im s-Zustand. In allen Einkristallen wachst α mit zunehmendem e0 uber die Maximumamplitude, und der Beginn des Plateaus wurde in beiden Zustanden beobachtet. Der Effekt ist mit nichtlinearen Phanomenen gekoppelt, welche bei deutlichen Loop-Ausbauchungen entstehen. Die Amplitudenabhangigkeit der Verluste, hervorgerufen durch diesen Effekt, wurde analysiert. Die Resultate dieser Analyse befinden sich in guter Ubereinstimmung mit den experimentellen Daten.

Measurement of the absorption of ultrasound in the critical region of lithium-ammonia solutions as a function of concentration, frequency, and temperature are presented. The absorption reaches a maximum at 4.2 mole percent lithium and is a function of the frequency. The frequency dependence can be explained either by a single relaxation at around 20 MHz or by using Fixman's theory with a correlation length of 51.3 A.

Ultrasonic and P-V-T measurements have been combined to derive a complete thermodynamic description of liquid benzene in the temperature range from 300 to 465 K and in the density range from 9.1 to 11.3 mol l −1 .

Excess molar volumes VmE and ultrasonic speeds are reported for (3,6-dioxaoctane + n-heptane) at 298.15 K, and are used to calculate isentropic compressibilities and the differential coefficients ( ∂V m E ∂p ) s . The results are compared with those obtained previously for other (ether + n-heptane) mixtures and their interpretation in terms of the Flory theory is examined.