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Flowering plants have evolved an extraordinary variety of signalling traits to attract their pollinators. Most flowers rely on visual and chemical signals, but some bat-pollinated plants have evolved passive acoustic floral signals. All known acoustic flower signals rely on the same principle of increased sonar reflectivity. Here, we describe a novel mechanism that relies on increased absorption of the area surrounding the flower. In a bat-pollinated cactus (Espostoa frutescens) we found a hairy inflorescence zone, a so-called cephalium. Flowers solely emerge out of this zone. We measured the echoes of cephalia, flowers and unspecialized column surfaces and recorded echolocation calls of approaching bats. We found that the cephalium acts as a strong ultrasound absorber, attenuating the sound by −14 dB. The absorption was highest around the echolocation call frequencies of approaching bats. Our results indicate that, instead of making flowers more reflective, plants can also evolve structures to attenuate the background echo, thereby enhancing the acoustic contrast with the target.

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.

У класичній роботі Штерна і Гранато вивчались частотні спектри дислокаційного поглинання ультразвуку Δd(f) на зразках високочистої міді. Цими авторами було зафіксовано нестандартну особливість у поведінці кривих Δd(f) у дослідах з опроміненими кристалами – їх високочастотні асимптоти накладаються одна на одну, що докорінно відрізняється від тих результатів, що отримані у дослідах, де вивчається аналогічні характеристики в умовах зміни температури і густини дислокацій зразків. Зважаючи на відсутність у літературі будь-яких тлумачень цього експериментального факту і фізичного описання картини процесу дислокаційного поглинання ультразвуку в опромінених кристалах, у даній роботі було поставлено за мету проаналізувати новітні результати з вказаного напрямку і дати пояснення вказаній особливості, що спостерігається на експерименті. Надаються рекомендації, що можуть бути корисними при проведенні акустичних досліджень кристалів з домішками і центрами закріплення магнітної природи. The classical work of Stern and Granato studied the frequency spectra of the dislocation absorption of ultrasound Δd(f) for samples of high-purity copper. These authors recorded a non-standard feature in the behavior of the curves Δd(f) in experiments with irradiated crystals – their high-frequency asymptotes are superimposed on one another, which is fundamentally different from those obtained in experiments where similar characteristics are studied under conditions of change in temperature and density of samples' dislocations. In view of the absence of this experimental fact interpretation in special literature and as there were no physical description of dislocation absorption of ultrasound process in irradiated crystals, this paper was intended to analyze the latest studies' results in this area and give an explanation of this particular feature that was observed in the experiment. There are recommendations that can be useful in conducting acoustic exploration of crystals with impurities and pinning centers of magnetic nature.

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 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).

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.

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 .

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...

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.

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.

Laser ultrasonics is combined with the reverberation technique to measure ultrasound absorption during thermal cycles applied to medium-carbon steel samples. During heating to the austenitic phase, a small Snoek peak is observed around 360 °C at 10 MHz along with a signature of the ferromagnetic to paramagnetic transition near 768 °C. Upon cooling, the behavior of the internal friction is much different from that of heating: reduced high-temperature absorption, delayed phase transition, smaller magnetoelastic contribution and stronger Snoek peak are observed. The austenitizing temperature is found to have primary importance on the internal friction behavior during cooling. These measurements show that ultrasound absorption measurements using laser ultrasonics could serve as a basis for a technique to characterize the microstructure evolution of steel in various temperature ranges., 13th International Conference on Internal Friction and Ultrasonic Attenuation in Solids, Bilbao, Spain, July 8-12, 2002, Bilbao, Spain

The beam deflection method has been used for the detection of ultrasound absorption in a plane sample of silicon rubber which in a water bath is exposed to a beam of ultrasound. Parallel scanning of the laser beam across the pump beam cross section yields the acoustic power transmitted to the absorber. Measurements in dependence on ultrasound frequency show the mirage signal to correlate well with the absorption coefficient of the material.

The influence of crystal defects and ultrasound absorption on X-ray diffraction under the condition of X-ray acoustic resonance are theoretically investigated. It is shown that the rocking curve and integral intensity of diffraction are very sensitive to defect's type and concentration.

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.

Abstract The entropy production of tumorous cells is higher than that of normal cells, and entropy flow is therefore directed from tumorous toward healthy cells. This results in information concerning the cancer propagating into the surrounding normal tissue. However, ultrasound absorption results in additional entropy production in tissues. The entropy mechanism possibly provides a basis for a novel approach to anticancer therapy through the use of ultrasound irradiation. Methods Through the calculation of ultrasound-induced entropy production and comparison of the theoretical results with the experimental data on ultrasound absorption in biological tissues, we have demonstrated that ultrasound absorption will increase the entropy in normal tissue more efficiently than in tumorous tissue due to the more acidic nature of the latter. Consequently, the direction of entropy flow between these two kinds of cells may be reversed on exposure to ultrasound. Conclusion The higher entropy accumulation of normal cells during ultrasound irradiation may possibly lead to a change in the original direction of entropy flow and avoid the propagation of information on the cancer into the normal tissues. We suggest that low-intensity, low-frequency ultrasound irradiation may be an efficient tool for the therapy of solid tumors.

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.

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.

The speed of sound, measured by a pulse-echo-overlap method, was determined for {(1 − x)CCL 4 + xc -C 6 F 11 CF 3 } along several paths close to the critical solution point. Determinations along the coexistence curve, where x exceeds the critical mole fraction, were carried out for nine different frequencies from 2.21 to 3.05 MHz. Evaluation of the critical exponent β from the results was investigated.

An optical device based on the Debye-Sears effect is developed to determine the ultrasonic absorption and velocity in molten alkali nitrate + silver nitrat mixtures. RbNO3 + AgNO3 and CsNO3 + AgNO3 are investigated in the total composition range between 480 K and 580 K within a frequency interval from 10 MHz to 35 MHz. In the concentration range of high ultrasonic absorption we find dispersion and a frequency dependent step in the absorption curve caused by relaxation. The relaxation time of the structural relaxation in the molten salt mixtures investigated here is in the order of 10-8 s. The volume viscosity, the adiabatic constant, and the compressibilities are calculated.

Speeds of sound and densities of { x C 7 H 16 + (1 − x )C 6 H 6 } were measured at 293.15 and 303.15 K. Isentropic compressibilities of the mixture were estimated from the results. Excess isentropic compressibilities were anomalous being S-shaped with x .

Ultrasound absorption has been measured in pure trifluoroacetic acid and its approximately equimolar mixture with acetic acid (51.5 mole% of acetic acid) at 20, 30, 40, and 50 °C and atmospheric pressure over the frequency range 3 - 57 MHz. The absorption curve of trifluoroacetic acid could be flitted by a single relaxation step (relaxation frequency 3.5 - 11 MHz, low frequency absorption about one tenth of that of acetic acid), whereas the equimolar mixture followed a two step relaxation curve (lower relaxation frequency 1.5 - 3 MHz, absorption correspondingly higher than in pure trifluoroacetic acid, higher relaxation frequency 12.5 - 39 MHz, absorption about 3% of the low frequency absorption).

activity or a turn of about 180 ~ may be observed. Therefore we have again good reason for concluding that all the activities of the gravioscilloscope and the systematic variations in the ultraoptic orientation of Melolontha are a consequence of the continuously shifting of the GWWpattern. Magnetically polarized magnetite crystals yielded five times surprising results at new moon and full moon. The curves indicating the direction of the float at intervals of 5 to 2 V2 min showed double spikes at the moment when the Experientia 41 (1985), Birkhguser Verlag, CH~4010 Basel/Switzerland

Ultrasound absorption has been measured in binary mixtures of phenol with carbontetrachloride and cyclohexane covering the complete concentration range at 20, 30, 40, and 50 °C. Absorption maxima in dilute phenolic solutions are interpreted as arising from cyclic association of phenol to trimers or tetramers.

Le comportement de microemulsions constituees de toluene, eau salee (NaCl), dodecylsulfate de sodium et butanol a ete etudie en fonction de la salinite. L'augmentation de la salinite se traduit par des transitions de phase de type Winsor I→Winsor III et Winsor III→Winsor II aux salinites S 1 =5,5 et S 2 =8 g NaCl/100 g d'eau respectivement. Aux salinites S 1 et S 2 on observe une divergence de la birefringence d'ecoulement qui revele un ordre orientationnel important dans/ou entre les gouttelettes de microemulsions. L'absorption ultrasonore ne montre de variation importante qu'au voisinage de S 2 , salinite pour laquelle un comportement de type critique a ete observe en diffusion elastique et quasi-elastique de la lumiere. Cette variation a ete attributee a un couplage entre les ondes ultrasonores et l'equilibre de fusion-fission des gouttelettes. Dans le domaine de salinite compris entre S 1 et S 2 (systemes de type Winsor III) les resultats d'absorption ultrasonore et de birefringence d'ecoulement suggerent une structure particuliere de la phase microemulsion

Studies of the bulk ultrasonic properties of intact tissues reveal the importance of biomacromolecules in determination of ultrasonic absorption. The absorption coefficient of blood has been found to be proportional to the weight percentage of the protein content, which has encouraged studies of the absorption by proteins and their analogs in solution. Studies of amino acids, polyamino acids, and soluble proteins in aqueous solution have suggested such mechanisms as relaxation of proton‐transfer equilibria occurring at ionizable residues and relaxation of solvent‐solute equilibria. Though other mechanisms have been proposed, no single mechanism appears to be predominant in being responsible for ultrasonic absorption by proteins.

The ultrasound absorption coefficient in fresh excised rat liver has been obtained at 1‐MHz fundamental frequency in the intensity range (SPTP) from low intensity (50 W cm−2) to high intensity (800 W cm−2). At atmospheric pressure the pressure absorption coefficient starts at 0.035 (50 W cm−2) and rises to 0.090 (800 W cm−2). Theoretical calculations over this same intensity range show agreement in the shape of the absorption coefficient curve as a function of intensity up to approximately 450 W cm−2. Above this intensity the experimentally derived values flatten off and slightly decline with increasing intensity. The theory shows no such characteristic. The absorption coefficient was also measured in the same intensity range at a pressure of 350 lb in.−2. (This pressure provides a bias for 193 W cm−2 at 1 MHz.) There is a small (10%) and statistically significant reduction in the absorption coefficient in the intensity range from 200–500 W cm−2 but below and above this range there is no statistically sig...

It has been known for decades that ultrasound is capable of producing physiological change in man and in laboratory animals. A dominant mechanism for the change is temperature elevation resulting from sound absorption. It has been shown for some situations that the processes for heat generation and transport are understood well enough to make it feasible to predict the temperature that results from specific acoustic exposures. Thus Pond, Robinson and Lele, Carstensen, Lizzi, and others have successfully calculated intensity‐time combinations required for production of recognizable lesions in mammalian tissues and other media. There is now special interest in computational methods for application to ultrasonic hyperthermia, and also to the formulation of safety criteria for diagnostic ultrasound. For the latter purpose a simplified method has been developed, based on a Green's function solution to the bio‐heat transfer equation. In this paper, previous work on temperature calculations is reviewed, and recent results discussed.