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Since Biot’s first work on acoustic waves in non-dissipative solid media, it has been known that the group velocity of bulk acoustic waves coincides with the velocity of wave energy transport. The recent studies on these types of velocities for electromagnetic waves reveal that (i) these can differ, and (ii) the superluminal group velocities may exist. The current research demonstrates that in the case of Lamb waves propagating in sandwich clamped–clamped plates, the group velocity can exceed the largest longitudinal bulk wave velocity, and, moreover, the group velocity can be infinitely large, similarly to electromagnetic waves.

A closed-form dispersion equation for Lamb waves is obtained for analyzing dispersion in functionally graded (FG) plates with arbitrary anisotropy and arbitrary transverse inhomogeneity. The dispersion equation is derived and analyzed by a variant of the sextic formalism, previously developed for Lamb waves propagating in anisotropic layered plates with homogeneous layers. For the case of FG plates with transverse asymmetric inhomogeneity, some peculiarities in dispersion of the fundamental flexural Lamb mode are observed, revealing discrepancy in asymptotic behavior at high frequencies between homogeneous and FG isotropic plates.

A family of one parametric infinitely differentiable hyperelastic potentials for three-dimensional infinitesimal problems of bimodular isotropic materials is constructed, yielding a set of uniform approximations to the discontinuous stepwise elastic modulus adopted in the original one-dimensional bimodular formulation. The introduced potentials enable either analytical solutions or construction of the explicit governing equations for a number of static and dynamic problems. Theorem of convergence to the discontinuous bimodular modulus is proved.

It is known that an incident bulk P wave propagating in a homogeneous isotropic halfspace, being reflected from the plane boundary, may exhibit a mode conversion into shear S wave without the formation of reflected P waves. The mode conversion takes place, when the incident wave hits the boundary at some critical angles, which depend upon Poisson’s ratio. Herein, it is revealed that the Jeffreys solution for the mode conversion angles needs in in corrections, mainly because of spurious roots, appeared at solving a specially constructed eighth-order polynomial for the P wave reflection coefficient. The developed approach allowed us to construct a bi-cubic polynomial and obtain analytical expressions for its roots, and to find correct values for angles of incidence, at which the mode conversion occurs.

It is known that Lamb waves in homogeneous traction-free plates can propagate with arbitrary phase velocity, spanning the admissible speed interval (0; + ∞ ) . However, as the current research shows, Lamb waves propagating in two-layered traction-free plates may have ‘forbidden’ phase velocities, at which no Lamb waves can propagate. The analysis is based on the approach comprising Cauchy complex formalism and the exponential fundamental matrix method.

It is revealed that a hyperelastic material with smooth variation of elastic properties with strain, may serve as an acoustic black hole in respect of harmonic elastic waves. The analysis comprises theoretical method based on thermodynamic analysis, Cauchy formalism, coupled with numerical method utilizing Lax–Wendroff explicit numerical scheme in time domain and finite element discretization in spatial domain. The observed phenomena elucidate the appearance of ABH in hyperelastic media and may be indispensible for development of new types of vibration and shock absorbers, which result in mechanical energy attenuation in a purely elastic system.

For the first time, velocity gaps in the dispersion portraits of guided waves propagating in functionally graded (FG) traction-free plates were revealed, meaning appearance of the “forbidden” phase velocity range where guided waves do not exist. The observed phenomenon does not occur in homogeneous isotropic or anisotropic plates. The analysis is based on the modified Cauchy sextic formalism and exponential matrix method. The presence of “forbidden” phase velocities may be essential in the non-destructive diagnostics of functionally graded media by acoustic methods along with applications in theoretical geophysics.

The dispersion relations are derived for SH waves in stratified anisotropic plates with arbitrary elastic anisotropy. Analytical expressions for vectorial group and ray velocities of SH waves propagating in anisotropic layers with monoclinic symmetry are obtained. Closed-form relations between velocities and specific kinetic and strain energy for SH waves are derived and analyzed.

Recombineering is an efficient method of in vivo genetic engineering applicable to chromosomal as well as episomal replicons in Escherichia coli . This method circumvents the need for most standard in vitro cloning techniques. Recombineering allows construction of DNA molecules with precise junctions without constraints being imposed by restriction enzyme site location. Bacteriophage homologous recombination proteins catalyze these recombineering reactions using double- and single-stranded linear DNA substrates, so-called targeting constructs, introduced by electroporation. Gene knockouts, deletions and point mutations are readily made, gene tags can be inserted and regions of bacterial artificial chromosomes or the E. coli genome can be subcloned by gene retrieval using recombineering. Most of these constructs can be made within about 1 week's time.

It has been found that highly porous organic foams (hyperfoams) modeled by the Blatz–Ko and Hill hyperelastic potentials may exhibit mechanical energy loss caused by the formation and propagation of strain discontinuities arising when a portion of a faster wave pulse overtakes a slower one. This observation opens up a possibility for creating a new type of shock absorbers containing no viscous or dry friction elements. For example, the considered Blatz–Ko-type hyperelastic potential is a good material behavior model for moderately stiff polyurethane (PU) foams both at large compression and at large extension strains. The analysis utilizes a combined method consisting of the explicit time integration technique coupled with the finite element method for spatial discretization.