[en] The Davydov model for a one-dimensional protein, coupling the high-frequency amide-I vibration to longitudinal-acoustic phonons, is investigated by use of finite-temperature molecular dynamics. Soliton dynamics is studied in both equilibrium and nonequilibrium situations. The random thermal motions prevent self-trapping from occurring at temperatures of interest for transport in real proteins. 9 references, 2 figures, 1 table

[en] We indicate some of the emerging thematic connections between strongly nonlinear effects in condensed matter and biological materials. These are illustrated with model studies of: (1) structural phase transitions in anisotropic lattices; and (2) finite temperature effects on self-trapped states in vibron-phonon models of α-helix proteins. 13 refs., 8 figs

[en] Long-time Langevin dynamics simulations of large (N x N, N = 128) 2-dimensional arrays of Josephson junctions in a uniformly frustrating external magnetic field are reported. The results demonstrate: Relaxation from an initially random flux configuration as a ''universal'' fit to a ''glassy'' stretched-exponential type of relaxation for the intermediate temperatures T (0.3 T_c approx-lt T approx-lt 0.7 T_c), and an ''activated dynamic'' behavior for T ∼ T_c A glassy (multi-time, multi-length scale) voltage response to an applied current. Intrinsic dynamical symmetry breaking induced by boundaries as nucleation sites for flux lattice defects gives rise to transverse and noisy voltage response

[en] Within the Su, Schrieffer and Heeger model we have calculated, both analytically and numerically, the effects of model impurities on the electronic structure and lattice distortion of trans-polyacetylene. We find that the electron-phonon coupling may result in a fundamental alteration of the impurity level location. In simulated photoexcitation experiments on the defected system we find that, in addition to the kinks and breathers produced in the undefected system, ''trapped kinks'', excitons and polarons may also be produced. We suggest that the polarons produced in this novel way may be unusually stable and play an important role in hopping conduction mechanisms

[en] The zero field steps in the current-voltage characteristic of Josephson tunnel junctions are explained as a manifestation of the oscillatory motion of N solitons in the tunnelling barrier, where N is the step number. The solitons evolve according to a perturbed sine-Gordon equation and numerical solutions of this equation explain the zero field steps as well as many features of the emitted microwave radiation. (Auth.)

[en] This paper reports on time resolved shock-wave measurements have often been used to infer microstructural behavior in crystalline solids. The authors apply this approach to an interpretation of the release-wave response of an aluminum alloy (6061-T6) as it is dynamically unloaded from a shock-compressed state of 20.7 GPa. The anelastic behavior in the initial portion of the unloading wave is attributed to the accumulation of internal stresses created by the shock process. Specific internal-stress models which are investigated are the double pile-up, the single pile-up, and single dislocation loops between pinning points. It is found that the essential characteristics of double and single pile-ups can be represented by a single dislocation between two pinned dislocations of like sing. Calculations of anelastic wave speeds at constant unloading strain rate are then compared with experimental data. The results suggest that the residual internal stress is due to pinned loops of density 10¹⁵M^-2, and the viscous drag coefficient in the shock-compressed state is on the order of 10^-7 MPa s (approximately two orders of magnitude greater than expected under ambient conditions)

[en] Cylindrically symmetric wave solutions to the nonlinear Schroedinger equation localized in a ring are investigated numerically. Outward waves expand towards infinity or reach a maximum size and shrink on the energy. Inward waves collapse in a finite time in agreement with the virial theorem. (orig.)

[en] Dislocation generation is studied in a generalized two-dimensional Frenkel-Kontorova model which allows consideration of dislocations of arbitrary Burgers vector and line shape. Two new mechanisms for dislocation generation at high stresses have been found: (1) heterogeneous nucleation of dislocations on preexisting dislocations and (2) generation of dislocation loops in the wake of a moving dislocation. These new mechanisms provide an understanding of how materials generate the density of dislocations required to accomodate arbitrary strains at high strain rates

[en] The equations of the Davydov model, which describe energy propagation along linear-chain molecules by a soliton mechanism, have heretofore been derived by a combination of quantum-mechanical and classical techniques. We give here a derivation which is completely based on quantum mechanics

[en] A detailed comparison between experiments and numerical calculations on fluxons in intermediate length Josephson tunnel junctions have shown that (i) the origin of zero field steps in junctions of length of order lambdasub(J) is the resonant oscillation of fluxons, (ii) that the fluxons in N-fluxon modes move in a bunched state on major portions of the steps, and (iii) that good qualitative agreement is achieved using a sine-Gordon model of the junction. (orig.)