acoustic radiation force

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Acoustic radiation force and torque on spheroidal particles in an ideal cylindrical chamber

Acoustic radiation force and torque on spheroidal particles in an ideal cylindrical chamber

3 Physical Acoustics Group, Instituto de F´ısica, Universidade Federal de Alagoas, Macei´ o, AL 57072- 970, Brazil (Dated: 21 September 2020) We theoretically investigate how the acoustic radiation force and torque arise on a small spheroidal particle immersed in a nonviscous fluid inside an ideal cylindrical chamber. The ideal chamber comprises a hard top and bottom (rigid boundary condition), and a soft or hard lateral wall. By assuming the particle is much smaller than the acoustic wavelength, we present analytical expressions of the radiation force and torque caused by an acoustic wave of arbitrary shape. Unlike previous results, these expressions are given relative to a fixed laboratory frame. Our model is showcased for analyzing the behavior of an elongated metallic microspheroid (with a 10 : 1 aspect ratio) in a half-wavelength acoustofluidic chamber with a few millimeters diameter. The results show the radiation torque aligns the microspheroid along the nodal plane, and the radiation force causes a translational motion with a speed of up to one body length per second. At last, we discuss the implications of this study to propelled nanorods by ultrasound.
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Mathematical modelling of Acoustic Radiation Force in transient shear wave elastography in the heart

Mathematical modelling of Acoustic Radiation Force in transient shear wave elastography in the heart

3 Current affiliation: Computational Cardiology Laboratory, Institute of Biophysics, Medical University of Graz, Austria Abstract The aim of this work is to provide a mathematical model and analysis of the excitation and the resulting shear wave propagation in Acoustic Radiation Force (ARF)-based shear wave cardiac elastography. Our approach is based on asymptotic analysis; more precisely, it consists in considering a family of problems, parametrised by a small parameter inversely proportional to the excitation frequency of the probes, the viscosity and the velocity of pressure wave propagation. We derive a simplified model for the expression of the ARF by investigating the limit behaviour of the solution when the small parameter goes to zero. By formal asymptotic analysis - an asymptotic expansion of the solution is used - and energy analysis of the nonlinear elastodynamic problem, we show that the leading- order term of the expansion is solution of the underlying, incompressible, nonlinear cardiac mechanics. Subsequently, two corrector terms are derived. The first is a fast-oscillating pressure wave generated by the probes, solution of a Helmholtz equation at every time. The second corrector term consists in an elastic field with prescribed divergence, having a function of the first corrector as a source term. This field corresponds to the shear acoustic wave induced by the ARF. We also confirm that, in cardiac mechanics, the presence of viscosity in the model is essential to derive an expression of the shear wave propagation from the ARF, and that this phenomenon is related to the nonlinearity of the partial differential equation.
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Acoustic Radiation Force Impulse (ARFI) and Transient Elastography (TE) for evaluation of liver fibrosis in HIV-HCV co-infected patients.

Acoustic Radiation Force Impulse (ARFI) and Transient Elastography (TE) for evaluation of liver fibrosis in HIV-HCV co-infected patients.

Nora Frulio 1* , Hervé Trillaud 1 , Paul Perez 2 , Julien Asselineau 2 , Marianne Vandenhende 3 , Mojgan Hessamfar 3 , Fabrice Bonnet 3 , Florent Maire 1 , Jean Delaune 3 , Victor De Ledinghen 4,5 and Philippe Morlat 3 Abstract Background: Transient elastography (TE) is widely used for non-invasive assessment of liver fibrosis in HIV-HCV co-infected patients. TE, however, cannot determine liver morphology. Acoustic radiation force impulse (ARFI) imaging is a novel procedure enabling assessment of liver fibrosis during a conventional ultrasonographic examination. This study evaluated the correlation between liver fibrosis measurements by TE and ARFI.
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Correlating the Ultrasonic Thrust Force with Acoustic Streaming Velocity

Correlating the Ultrasonic Thrust Force with Acoustic Streaming Velocity

Examples of thrust generation by ultrasonic means can be found in airborne applications, where Parviz et al. [4], [5] used specially designed micro-thrusters mounted with ultrasonic membranes, to stream flow through an array of perforated holes, hence generating thrust. Underwater, Balamuth [6] used the concept of ultrasonic surface vibrations (Lamb wave) to excite a stator, which in turn rotates a rotor so as to produce thrust. Another example is found in the work of Saito et al. [7], where they utilize the acoustic radiation force generated from an ultrasonic transducer impinging on a small propeller to transfer energy. Rife et al. [8] attached a transducer externally onto a microfluidic, closed-loop chamber designed to pump or mix water, which is akin to microreactors found commercially. These applications, while generating flow by ultrasonic means, do not treat thrust as a direct locomotive agent for marine craft and only very few brief articles can be found addressing this idea [9], [10], [11].
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Chiral drag force

Chiral drag force

3 Drag force In this section we shall only consider µ L = µ R and shall therefore set κ = 0 and think of µ as representing the quark number chemical potential (µ L + µ R )/2. The drag force has been calculated in a static plasma with µ = 0 and no gradients in refs. [5–7]. The basic picture of heavy quark dynamics that emerges, with all but the initially most energetic heavy quarks being rapidly slowed by drag and then becoming trac- ers diffusing within the (moving) fluid, is qualitatively consistent with early experimental investigations [49]. For a review, see ref. [50]. Subsequently, the holographic calcula- tional techniques were generalized to any static plasmas whose gravitational dual has a 4+1-dimensional metric that depends only on the holographic (i.e. ‘radial’) coordinate in ref. [51] and heavy quark energy loss and diffusion has by now been investigated in the equilibrium plasmas of many gauge theories with gravitational duals [52–66]. In partic- ular, the drag force on a heavy quark in a static plasma with µ 6= 0 was calculated in refs. [51, 52]. We reproduce these results in section 3.1. More recently, the drag force on a heavy quark moving through the far-from-equilibrium matter present just after the collision of two sheets of energy density [67] has been calculated and compared to that in static strongly coupled plasma in equilibrium [68]. Motivated initially by the need to understand these results, in ref. [11] the drag force was computed in a fluid with µ = 0 in which there are spatial and temporal gradients in the fluid temperature and flow velocity, to leading order in these fluid gradients. In section 3.2, we shall reproduce these results and shall compute the leading order effects of fluid gradients in a strongly coupled N = 4 SYM plasma with µ 6= 0. (As an aside, we note that the effects of fluid gradients on photon emission have also been investigated [69].)
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Axial Casimir force

Axial Casimir force

We show that, in addition to the dissipative Casimir fric- tion, a dissipationless force can emerge for a rotating par- ticle near a PS or TS (or both) breaking BIMs. Since the dissipationless rotation-induced force is always parallel to the particle’s rotation axis and changes sign when its spinning direction is reversed, we, therefore, call it the axial Casimir force (ACF). Two cases are of particular interest: (i) When the rotation axis is parallel to the BIM plate, the axial Casimir force is lateral (L-ACF); (ii) when the rotation axis is perpen- dicular to the BIM plate, the axial Casimir force is vertical (V-ACF) (Fig. 1 ). We calculate ACF both numerically and analytically and show that TS breaking is crucial for V-ACF, whereas, by contrast, PS breaking is important for L-ACF. Let us observe that very recent experiments have already achieved a superfast rotation of nanoparticles, making the ACF within the experimental reach [ 14 ].
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LES of the aero-acoustic coupling in acoustic liners containing multiple cavities

LES of the aero-acoustic coupling in acoustic liners containing multiple cavities

and 3D case lead to a similar spectrum with a large peak at the resonance frequency close to 800H z, and a rapid decay of the energy for higher frequencies. Note that for the two configurations, the spectra are not changing significantly after the 51 st cavity, a results also obtained for the shape factor that was contant after the 21 th cavity, denoting the nature of the boundary layer was no more evolving. For further downstream location however, the PSD spectra are different depending on the 2D or 3D cases. In 2-dimension, a peak is observed at 454H z, which is much smaller than the resonance peak close to 750H z-800H z. Note that such a peak at a lower frequency was not obtained in the acoustic spectra for the 2D case. For frequencies higher than the peak frequency, two different regimes are obtained, typical of the double cascade encountered in 2D turbulent flows. The first regime corresponds to the energy flux regime characterized by a slope −5/3. The second regime is associated with the enstrophy flux, and is characterized by a slope close to −3. Boffetta and Musacchio [33] provide a more detailed analysis of this peculiar regime, concluding that this larger slope can be (i) either due to a lack of resolution of the small flow structures, and/or (ii) a viscous effect (i.e. Reynolds effect), since the slope −3 is obtained for a inviscid flow. For the viscosity ν used in the present simulation, the slope correction proposed by Boffetta and Musacchio [33] is δ ≈ 1.8. This value gives a slope −(3 + δ) in good agreement with the present results ( in Fig. 9, top right). In 3-dimension, the PSD spectra are different. First, the peak is observed at the resonance peak close to 800Hz. Moreover, the low-frequency modes are visible for all cavities, in particular the first cavity showing a strong peak close to 60Hz. For higher frequencies, the classical Kolmogorov cascade with a slope −5/3 is obtained. As a conclusion, these results demonstrates that a trace of the 60Hz mode is visible in the velocity fluctuations inside the shear layer. These perturbations, observed also at the first cavity, could have been excited by acoustic waves coming from the other cavities (since the incoming boundary layer steady in the present case, it cannot contribute to this frequency content).
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La force exclusive de la norme

La force exclusive de la norme

4. Exclusivité Je parviens enfin à la considération du dernier critère : l’exclusivité. Cumulant les critères précédents et sa spécificité propre, il explicite la nature de la contrainte à l’œuvre lorsque l’un des contenus normatifs qu’examine l’agent s’impose à lui. Considérant donc une alternative unilatérale et exhaustive, observons ensemble que sa force normative procède de ce que la structure qui l’oppose à une norme concurrente est une opposition de contradiction. Ce faisant, sa force est "exclusive" en tant qu’elle exclut les normes concurrentes qui lui sont contradictoires. Je rappelle l’énoncé canonique du principe aristotélicien de non-contradiction :
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COURS-Force-Centrale

COURS-Force-Centrale

On constate une très forte analogie entre l’expression de la force de gravité et celle de la force électrostatique. La grande différence réside dans le fait que la force électrostatique peut être répulsive ou attractive en fonction des signes des charges mises en jeu. La force de gravitation est toujours attractive car les masses sont toujours des grandeurs positives.

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Thermo-acoustic Instablilities

Thermo-acoustic Instablilities

1.1 Thermo-acoustic Instablilities By L. Gicquel F. Nicoud & T. Poinsot Thermo-acoustic instabilities arise from the coupling between acoustic waves and flames and can lead to high amplitude instabilities [1, 2, 3, 4]. In general, these instabilities induce oscillations of all physical quantities (pressure, velocities, temperature, etc.); in the most extreme cases, they can destroy the burner by inducing large amplitude flame motion (flashback) or unsteady pressure (material fatigue). Since the equivalence ratio oscillates when instabilities are present, there is a general trend for combustors to be more unstable when operating in the lean regime. Also, due to new inter- national constraints, pollutant emissions must be reduced and gas turbine manufacturers need to operate their systems under leaner and leaner condi- tions. Consequently, there is a need to understand combustion instabilities and to be able to predict them at the design level [5].
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Multi-modal acoustic-photo-acoustic imaging for small animal imaging

Multi-modal acoustic-photo-acoustic imaging for small animal imaging

/ La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. Access and use of [r]

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16-Force de Laplace

16-Force de Laplace

Introduction : Le magnétisme est un phénomène très important car il régit le fonctionnement des moteurs électriques, qui convertissent l’énergie électrique en énergie mécanique. En effet, nous allons voir que l’interaction entre un champ magnétique et un courant électrique créée une force, qui a un rôle moteur considérable.

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Effect to the capillary force on force measurements in submerged micromanipulations.

Effect to the capillary force on force measurements in submerged micromanipulations.

Tel: +33 (0) 381 402 810 - Fax: +33 (0) 381 402 809 Website: http://www.lab.cnrs.fr, E-mail: michael.gauthier@ens2m.fr Abstract— The subject of this article is to analyse the impact of liquid surface tension on force measurement in submerged micromanipulations. On the one hand, at the present, mechanical characterization of biological objects in biological liquid has significant interest. On the other hand, the reduction of the surface force, and adhesion forces in a submerged medium could be a good approach to perform reliable artificial objects mi- cromanipulations. In both cases, the micro-nano force measurement in a liquid is a great challenge. In case of a force sensor placed out of the liquid, the measurement is disturbed by the liquid surface tension. This article proposes an analysis of the disturbance of the surface tension on the force measurement. Some design rules are proposed to reduce disturbances. We shows that the major disturbances are induced by the contact angle hysteresis and a complete method is proposed to calculate these disturbances in a micromanipulation task.
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COURS-Force centrale

COURS-Force centrale

IV – Mouvement d’un point matériel soumis à la force de gravité 4.1 Hypothèse de l’étude Nous allons étudier le mouvement d’un point matériel de masse m (le satellite) soumis à la force de gravité d’un autre objet (l’astre attracteur) de masse M (à ne pas confondre avec M le nom du point matériel que l’on emploie habituellement). L’astre sera situé au centre du référentiel galiléen O et considéré comme immobile car on supposera que M ! m . Cette situation est une bonne approximation quand on veut décrire le mouvement des planètes autour du soleil ou de satellites autour de la Terre. En général, les états liés du satellite sont des ellipses mais quand M ! m , les ellipses deviennent des cercles. C’est pourquoi nous allons étudier uniquement les trajectoires circulaires. Dans ce cas également, la situation est une bonne approximation pour décrire le mouvement des planètes autour du soleil ou de satellites autour de la Terre.
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High-speed force spectroscopy: microsecond force measurements using ultrashort cantilevers

High-speed force spectroscopy: microsecond force measurements using ultrashort cantilevers

Received: 29 July 2019 / Accepted: 27 August 2019 # The Author(s) 2019 Abstract Complete understanding of the role of mechanical forces in biological processes requires knowledge of the mechanical properties of individual proteins and living cells. Moreover, the dynamic response of biological systems at the nano- and microscales span over several orders of magnitude in time, from sub-microseconds to several minutes. Thus, access to force measurements over a wide range of length and time scales is required. High-speed atomic force microscopy (HS-AFM) using ultrashort cantilevers has emerged as a tool to study the dynamics of biomolecules and cells at video rates. The adaptation of HS-AFM to perform high- speed force spectroscopy (HS-FS) allows probing protein unfolding and receptor/ligand unbinding up to the velocity of molec- ular dynamics (MD) simulations with sub-microsecond time resolution. Moreover, application of HS-FS on living cells allows probing the viscoelastic response at short time scales providing deep understanding of cytoskeleton dynamics. In this mini- review, we assess the principles and recent developments and applications of HS-FS using ultrashort cantilevers to probe molecular and cellular mechanics.
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Blackbody and blackbody radiation

Blackbody and blackbody radiation

incandescent. Examples of incandescent objects are fire, candles, carbon arcs, and tungsten- filament lamps. They emit radiation with approx- imately the same spectral power distribution as a blackbody but with an intensity reduced by a factor called the emissivity, e. If the emissivity does not vary with wavelength, the source is called a gray body or nonselective radiator. An incandescent tungsten-filament lamp is close to being a gray body with an emissivity of approx- imately 0.40 [ 7 ]. The temperature of a blackbody that is closest in color to this gray body source is often used as an index of its color. This is referred to as the correlated color temperature, T c . An
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Compressed quantitative acoustic microscopy

Compressed quantitative acoustic microscopy

Quantitative acoustic microscopy (QAM) is an imaging technology employed to investigate soft biological tissue at microscopic resolution by eliciting its mechanical property with very high frequency ultrasound [1]. Specifically, by processing RF echo data, QAM yields two-dimensional (2D) quantitative maps of the acoustical and mechanical properties of soft tissues. Therefore, QAM provides a novel contrast mechanism compared to histology photomicrographs and optical and electron microscopy images [2]. Currently, QAM requires a complete 2D raster scan of the sample to form Part of this work has been supported by the thematic trimester on image processing of the CIMI Labex, Toulouse, France, under grant ANR- 11-LABX-0040-CIMI within the program ANR-11-IDEX-0002-02 and by ProSmart Solutions, 6-12 Rue Andras Beck 92360 Meudon, France.
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Adaptive multigroup radiation diffusion

Adaptive multigroup radiation diffusion

The physical interpretation of equation 3.11 is that the time rate of change of monochromatic radiation momentum density for photons at frequency v is equal to the [r]

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Automatic acoustic guitar tuner

Automatic acoustic guitar tuner

This new concept will reduce the time needed to tune a guitar by using an electromechanical design to wind and unwind the strings to eventually reach the desired frequen[r]

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Radiation et autres facteurs climatiques

Radiation et autres facteurs climatiques

Figure 1. La première méthode utilisée pour minimiser les effets de la radiation consiste à utiliser des polymères qui ne l'absorbent pas. Comme on l'a exposé dans CBD 121F , il est difficile, sauf à l'échelle du laboratoire, d'obtenir une transparence complète. C'est ainsi que le polyéthylène, qui devrait être transparent aux rayons UV, se détériore rapidement lorsqu'il est exposé à l'extérieur. La seconde méthode consisterait à réaliser des polymères à partir de combinaisons d'éléments dont les forces de liaison dépassent l'énergie disponible dans la radiation solaire. La plupart des combinaisons de ce type produisent malheureusement des composés simples, mais non des polymères. Parmi les quelques polymères qu'on peut obtenir, beaucoup sont rapidement décomposés par les autres facteurs, eau et oxygène. Les possibilités de succès de cette méthode sont donc limitées. Les polymères les mieux connus de ce type sont probablement les silicones qui, comme l'indique la Figure 1, possèdent une charpente silicium- oxygène, avec groupes latéraux organiques. La liaison silicium-oxygène n'est brisée que par des radiations de longueur d'onde inférieure à 270 nm, qui ne parviennent pas à la surface de la terre. Les groupes organiques sont nécessaires pour que le matériau possède les propriétés exigées d'un polymère; en leur absence, on a simplement du quartz ou de la silice - SiO 2 . Les
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