Ultrasound-based cell sorting with microbubbles: A feasibility study.

The isolation and sorting of cells is an important process in research and hospital labs. Most large research and commercial labs incorporate fluorescently or magnetically labeled antibodies adherent to cell surface antigens for cell identification and separation. In this paper, a process is described that merges biochemical labeling with ultrasound-based separation.

Concentration of microparticles and bubbles in standing waves.

This paper studies the collective dynamics of microparticles in plane and cylindrical resonators. Based on the known results regarding the motion of a single particle under the action of acoustic radiation force, concentration and separation of particles in standing waves are investigated. As an example, spherical particles (cells) with a slightly larger density and sound speed than those in ambient fluid are considered.

Stirring and mixing of liquids using acoustic radiation force.

The possibility of using acoustic radiation force in standing waves for stirring and mixing small volumes of liquids is theoretically analyzed. The principle of stirring considered in this paper is based on moving the microparticles suspended in a standing acoustic wave by changing the frequency so that one standing wave mode is replaced by the other, with differently positioned minima of potential energy. The period-average transient dynamics of solid microparticles and gas microbubbles is considered, and simple analytical solutions are obtained for the case of standing waves of variable amplitude.

Radiation force and shear motions in inhomogeneous media.

An action of radiation force induced by ultrasonic beam in waterlike media such as biological tissues (where the shear modulus is small as compared to the bulk compressibility) is considered. A new, nondissipative mechanism of generation of shear displacement due to a smooth (nonreflecting) medium inhomogeneity is suggested, and the corresponding medium displacement is evaluated. It is shown that a linear primary acoustic field in nondissipative, isotropic elastic medium cannot excite a nonpotential radiation force and, hence, a shear motion, whereas even smooth inhomogeneity makes this effect possible.

Internal solitons in the ocean and their effect on underwater sound.

Nonlinear internal waves in the ocean are discussed (a) from the standpoint of soliton theory and (b) from the viewpoint of experimental measurements. First, theoretical models for internal solitary waves in the ocean are briefly described. Various nonlinear analytical solutions are treated, commencing with the well-known Boussinesq and Korteweg-de Vries equations.

Solitons in nonintegrable systems.

We introduce the concept of this special focus issue on solitons in nonintegrable systems. A brief overview of some recent developments is provided, and the various contributions are described. The topics covered in this focus issue are the modulation of solitons, bores, and shocks, the dynamical evolution of solitary waves, and existence and stability of solitary waves and embedded solitons.

Wave interaction in acoustic resonators with and without hysteresis.

Nonlinear interaction of counterpropagating waves in solids is considered by using a general approach taking into account only the cumulative (resonant) nonlinear perturbations giving a nonzero contribution over the period and, consecutively, potentially able to significantly modify the linear solution. Different stress-strain relations are addressed, including those with hysteresis which serve as basic models for the recent acoustic experiments with rock and metals. An important case of the interaction of counterpropagating waves with close amplitudes in a high-Q resonator (bar) with hysteresis is specially addressed and compared with the case of a ring resonator.

Optical solitons: Perspectives and applications.

This article serves as an introduction to the focus issue on optical solitons. After a short review of the history of solitons and the field of integrable systems, a brief overview of the development of nonlinear optics and optical solitons is provided. Next, the various contributions to this focus issue are presented, and a few separate remarks are devoted to optical communications, where solitons promise to play a decisive role in the next generation of commercial systems.

Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea.

The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer.